Fix bug causing incorrect parsing of inputs with negative signs.

Make sure the set and define operators have the lowest precedence.

core/src/main/java/org/nwapw/abacus/lexing/Lexer.java

@@ -1,7 +1,7 @@
 package org.nwapw.abacus.lexing;
 
-import org.nwapw.abacus.lexing.pattern.nodes.EndNode;
 import org.nwapw.abacus.lexing.pattern.Pattern;
+import org.nwapw.abacus.lexing.pattern.nodes.EndNode;
 import org.nwapw.abacus.lexing.pattern.nodes.PatternNode;
 
 import java.util.*;
@@ -79,10 +79,10 @@ public class Lexer<T> {
 
             index++;
         }
-        matches.sort((a, b) -> compare.compare(a.getType(), b.getType()));
         if (compare != null) {
-            matches.sort(Comparator.comparingInt(a -> a.getContent().length()));
+            Collections.sort(matches, (a, b) -> compare.compare(a.getType(), b.getType()));
         }
+        Collections.sort(matches, (o1, o2) -> o1.getContent().length() - o2.getContent().length());
         return matches.isEmpty() ? null : matches.get(matches.size() - 1);
     }
 
@@ -136,7 +136,10 @@ public class Lexer<T> {
 
         @Override
         public int hashCode() {
-            return Objects.hash(name, id);
+            return Arrays.hashCode(new Object[] {
+                    this.name,
+                    this.id
+            });
         }
 
         @Override

core/src/main/java/org/nwapw/abacus/lexing/pattern/Pattern.java

@@ -6,7 +6,6 @@ import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Stack;
-import java.util.function.Function;
 
 /**
  * A pattern that can be compiled from a string and used in lexing.
@@ -36,8 +35,8 @@ public class Pattern<T> {
      * A map of regex operator to functions that modify a PatternChain
      * with the appropriate operation.
      */
-    private Map<Character, Function<PatternChain<T>, PatternChain<T>>> operations =
-            new HashMap<Character, Function<PatternChain<T>, PatternChain<T>>>() {{
+    private Map<Character, Transformation<T>> operations =
+            new HashMap<Character, Transformation<T>>() {{
                 put('+', Pattern.this::transformPlus);
                 put('*', Pattern.this::transformStar);
                 put('?', Pattern.this::transformQuestion);
@@ -207,7 +206,7 @@ public class Pattern<T> {
             if (operations.containsKey(currentChar)) {
                 if (currentChain == null) return null;
 
-                currentChain = operations.get(currentChar).apply(currentChain);
+                currentChain = operations.get(currentChar).transform(currentChain);
                 fullChain.append(currentChain);
                 currentChain = null;
                 index++;

core/src/main/java/org/nwapw/abacus/lexing/pattern/Transformation.java

@@ -0,0 +1,16 @@
+package org.nwapw.abacus.lexing.pattern;
+
+/**
+ * An interface that transforms a pattern chain into a different pattern chain.
+ * @param <T> the type used to identify the nodes in the pattern chain.
+ */
+public interface Transformation<T> {
+
+    /**
+     * Performs the actual transformation.
+     * @param from the original chain.
+     * @return the resulting chain.
+     */
+    PatternChain<T> transform(PatternChain<T> from);
+
+}

core/src/main/java/org/nwapw/abacus/parsing/standard/LexerTokenizer.java

@@ -20,7 +20,7 @@ public class LexerTokenizer implements Tokenizer<Match<TokenType>>, PluginListen
     /**
      * Comparator used to sort the tokens produced by the lexer.
      */
-    protected static final Comparator<TokenType> TOKEN_SORTER = Comparator.comparingInt(e -> e.priority);
+    protected static final Comparator<TokenType> TOKEN_SORTER = (o1, o2) -> o1.priority - o2.priority;
 
     /**
      * The lexer instance used to turn strings into matches.

core/src/main/java/org/nwapw/abacus/plugin/NumberImplementation.java

@@ -1,10 +1,10 @@
 package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.number.promotion.PromotionFunction;
 
 import java.util.HashMap;
 import java.util.Map;
-import java.util.function.Function;
 
 /**
  * A class that holds data about a number implementation.
@@ -14,7 +14,7 @@ public abstract class NumberImplementation {
     /**
      * The list of paths through which this implementation can be promoted.
      */
-    private Map<String, Function<NumberInterface, NumberInterface>> promotionPaths;
+    private Map<String, PromotionFunction> promotionPaths;
     /**
      * The implementation class for this implementation.
      */
@@ -41,7 +41,7 @@ public abstract class NumberImplementation {
      *
      * @return the map of documentation paths.
      */
-    public final Map<String, Function<NumberInterface, NumberInterface>> getPromotionPaths() {
+    public final Map<String, PromotionFunction> getPromotionPaths() {
         return promotionPaths;
     }
 

core/src/main/java/org/nwapw/abacus/plugin/Plugin.java

@@ -1,6 +1,7 @@
 package org.nwapw.abacus.plugin;
 
-import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
 import org.nwapw.abacus.function.interfaces.NumberFunction;
 import org.nwapw.abacus.function.interfaces.NumberOperator;
 import org.nwapw.abacus.function.interfaces.TreeValueFunction;

core/src/main/java/org/nwapw/abacus/plugin/PluginManager.java

@@ -1,7 +1,8 @@
 package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.Abacus;
-import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
 import org.nwapw.abacus.function.interfaces.NumberFunction;
 import org.nwapw.abacus.function.interfaces.NumberOperator;
 import org.nwapw.abacus.function.interfaces.TreeValueFunction;

core/src/main/java/org/nwapw/abacus/plugin/standard/StandardPlugin.java

@@ -1,12 +1,15 @@
 package org.nwapw.abacus.plugin.standard;
 
+import org.jetbrains.annotations.NotNull;
 import org.nwapw.abacus.context.MutableEvaluationContext;
-import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.context.PluginEvaluationContext;
+import org.nwapw.abacus.function.Documentation;
+import org.nwapw.abacus.function.DocumentationType;
 import org.nwapw.abacus.function.interfaces.NumberFunction;
 import org.nwapw.abacus.function.interfaces.NumberOperator;
 import org.nwapw.abacus.function.interfaces.TreeValueOperator;
-import org.nwapw.abacus.number.standard.NaiveNumber;
 import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.number.standard.NaiveNumber;
 import org.nwapw.abacus.number.standard.PreciseNumber;
 import org.nwapw.abacus.plugin.NumberImplementation;
 import org.nwapw.abacus.plugin.Plugin;
@@ -118,12 +121,12 @@ public class StandardPlugin extends Plugin {
      */
     public static final NumberFunction FUNCTION_ABS = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return params[0].multiply(context.getInheritedNumberImplementation().instanceForString(Integer.toString(params[0].signum())));
         }
     };
@@ -132,12 +135,12 @@ public class StandardPlugin extends Plugin {
      */
     public static final NumberFunction FUNCTION_LN = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1 && params[0].compareTo(context.getInheritedNumberImplementation().instanceForString("0")) > 0;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberImplementation implementation = context.getInheritedNumberImplementation();
             NumberInterface param = params[0];
             NumberInterface one = implementation.instanceForString("1");
@@ -165,10 +168,12 @@ public class StandardPlugin extends Plugin {
         /**
          * Returns the partial sum of the Taylor series for logx (around x=1).
          * Automatically determines the number of terms needed based on the precision of x.
+         *
+         * @param context
          * @param x value at which the series is evaluated. 0 < x < 2. (x=2 is convergent but impractical.)
          * @return the partial sum.
          */
-        private NumberInterface getLogPartialSum(MutableEvaluationContext context, NumberInterface x) {
+        private NumberInterface getLogPartialSum(PluginEvaluationContext context, NumberInterface x) {
             NumberImplementation implementation = context.getInheritedNumberImplementation();
             NumberInterface maxError = x.getMaxError();
             x = x.subtract(implementation.instanceForString("1")); //Terms used are for log(x+1).
@@ -213,12 +218,12 @@ public class StandardPlugin extends Plugin {
      */
     public static final NumberFunction FUNCTION_RAND_INT = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return context.getInheritedNumberImplementation().instanceForString(Long.toString(Math.round(Math.random() * params[0].floor().intValue())));
         }
     };
@@ -231,12 +236,12 @@ public class StandardPlugin extends Plugin {
      */
     public static final NumberFunction FUNCTION_SQRT = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return OP_CARET.apply(context, params[0], context.getInheritedNumberImplementation().instanceForString(".5"));
         }
     };
@@ -246,12 +251,12 @@ public class StandardPlugin extends Plugin {
      */
     public static final NumberFunction FUNCTION_EXP = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberImplementation implementation = context.getInheritedNumberImplementation();
             NumberInterface maxError = params[0].getMaxError();
             int n = 0;
@@ -284,12 +289,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionSin = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberImplementation implementation = context.getInheritedNumberImplementation();
             NumberInterface pi = piFor(params[0].getClass());
             NumberInterface twoPi = pi.multiply(implementation.instanceForString("2"));
@@ -309,12 +314,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionCos = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return functionSin.apply(context, piFor(params[0].getClass()).divide(context.getInheritedNumberImplementation().instanceForString("2"))
                     .subtract(params[0]));
         }
@@ -324,12 +329,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionTan = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return functionSin.apply(context, params[0]).divide(functionCos.apply(context, params[0]));
         }
     };
@@ -338,12 +343,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionSec = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return context.getInheritedNumberImplementation().instanceForString("1").divide(functionCos.apply(context, params[0]));
         }
     };
@@ -352,12 +357,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionCsc = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return context.getInheritedNumberImplementation().instanceForString("1").divide(functionSin.apply(context, params[0]));
         }
     };
@@ -366,12 +371,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionCot = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return functionCos.apply(context, params[0]).divide(functionSin.apply(context, params[0]));
         }
     };
@@ -381,13 +386,13 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionArcsin = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1
                     && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) <= 0;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberImplementation implementation = context.getInheritedNumberImplementation();
             if (FUNCTION_ABS.apply(context, params[0]).compareTo(implementation.instanceForString(".8")) >= 0) {
                 NumberInterface[] newParams = {FUNCTION_SQRT.apply(context, implementation.instanceForString("1").subtract(params[0].multiply(params[0])))};
@@ -415,12 +420,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionArccos = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) <= 0;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return piFor(params[0].getClass()).divide(context.getInheritedNumberImplementation().instanceForString("2"))
                     .subtract(functionArcsin.apply(context, params));
         }
@@ -431,12 +436,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionArccsc = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) >= 0;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberInterface[] reciprocalParamArr = {context.getInheritedNumberImplementation().instanceForString("1").divide(params[0])};
             return functionArcsin.apply(context, reciprocalParamArr);
         }
@@ -447,12 +452,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionArcsec = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1 && FUNCTION_ABS.apply(context, params[0]).compareTo(context.getInheritedNumberImplementation().instanceForString("1")) >= 0;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberInterface[] reciprocalParamArr = {context.getInheritedNumberImplementation().instanceForString("1").divide(params[0])};
             return functionArccos.apply(context, reciprocalParamArr);
         }
@@ -463,12 +468,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionArctan = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             NumberImplementation implementation = context.getInheritedNumberImplementation();
             if (params[0].signum() == -1) {
                 NumberInterface[] negatedParams = {params[0].negate()};
@@ -505,12 +510,12 @@ public class StandardPlugin extends Plugin {
      */
     public final NumberFunction functionArccot = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 1;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return piFor(params[0].getClass()).divide(context.getInheritedNumberImplementation().instanceForString("2"))
                     .subtract(functionArctan.apply(context, params));
         }
@@ -549,7 +554,7 @@ public class StandardPlugin extends Plugin {
      * @param x where the series is evaluated.
      * @return the value of the series
      */
-    private static NumberInterface sinTaylor(MutableEvaluationContext context, NumberInterface x) {
+    private static NumberInterface sinTaylor(PluginEvaluationContext context, NumberInterface x) {
         NumberInterface power = x, multiplier = x.multiply(x).negate(), currentTerm, sum = x;
         NumberInterface maxError = x.getMaxError();
         int n = 1;
@@ -568,7 +573,7 @@ public class StandardPlugin extends Plugin {
      * @param phi an angle (in radians).
      * @return theta in [0, 2pi) that differs from phi by a multiple of 2pi.
      */
-    private static NumberInterface getSmallAngle(MutableEvaluationContext context, NumberInterface phi, NumberInterface pi) {
+    private static NumberInterface getSmallAngle(PluginEvaluationContext context, NumberInterface phi, NumberInterface pi) {
         NumberInterface twoPi = pi.multiply(context.getInheritedNumberImplementation().instanceForString("2"));
         NumberInterface theta = FUNCTION_ABS.apply(context, phi).subtract(twoPi
                 .multiply(FUNCTION_ABS.apply(context, phi).divide(twoPi).floor())); //Now theta is in [0, 2pi).

core/src/main/kotlin/org/nwapw/abacus/Abacus.kt

@@ -1,15 +1,14 @@
 package org.nwapw.abacus
 
 import org.nwapw.abacus.config.Configuration
-import org.nwapw.abacus.context.MutableEvaluationContext
 import org.nwapw.abacus.context.EvaluationContext
+import org.nwapw.abacus.context.MutableEvaluationContext
 import org.nwapw.abacus.number.promotion.PromotionManager
+import org.nwapw.abacus.parsing.TreeBuilder
 import org.nwapw.abacus.parsing.standard.LexerTokenizer
 import org.nwapw.abacus.parsing.standard.ShuntingYardParser
-import org.nwapw.abacus.parsing.TreeBuilder
 import org.nwapw.abacus.plugin.PluginManager
 import org.nwapw.abacus.plugin.standard.StandardPlugin
-import org.nwapw.abacus.tree.standard.NumberReducer
 import org.nwapw.abacus.tree.nodes.TreeNode
 
 /**
@@ -47,7 +46,7 @@ class Abacus(val configuration: Configuration) {
     /**
      * The hidden, mutable implementation of the context.
      */
-    private val mutableContext = MutableEvaluationContext(numberImplementation = StandardPlugin.IMPLEMENTATION_NAIVE)
+    private val mutableContext = MutableEvaluationContext(numberImplementation = StandardPlugin.IMPLEMENTATION_NAIVE, abacus = this)
     /**
      * The base context from which calculations are started.
      */
@@ -64,13 +63,13 @@ class Abacus(val configuration: Configuration) {
      * Reloads the Abacus core.
      */
     fun reload(){
-        pluginManager.reload()
-        with(mutableContext) {
-            numberImplementation = pluginManager.numberImplementationFor(configuration.numberImplementation)
-                    ?: StandardPlugin.IMPLEMENTATION_NAIVE
+        with(mutableContext){
             clearVariables()
             clearDefinitions()
         }
+        pluginManager.reload()
+        mutableContext.numberImplementation = pluginManager.numberImplementationFor(configuration.numberImplementation)
+                ?: StandardPlugin.IMPLEMENTATION_NAIVE
     }
     /**
      * Merges the current context with the provided one, updating
@@ -106,9 +105,8 @@ class Abacus(val configuration: Configuration) {
      * @return the evaluation result.
      */
     fun evaluateTreeWithContext(tree: TreeNode, context: MutableEvaluationContext): EvaluationResult {
-        val newReducer = NumberReducer(this, context)
-        val evaluationValue = tree.reduce(newReducer)
-        return EvaluationResult(evaluationValue, newReducer.context)
+        val evaluationValue = tree.reduce(context)
+        return EvaluationResult(evaluationValue, context)
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/context/EvaluationContext.kt

@@ -1,5 +1,6 @@
 package org.nwapw.abacus.context
 
+import org.nwapw.abacus.Abacus
 import org.nwapw.abacus.number.NumberInterface
 import org.nwapw.abacus.plugin.NumberImplementation
 import org.nwapw.abacus.tree.Reducer
@@ -13,11 +14,11 @@ import org.nwapw.abacus.tree.nodes.TreeNode
  *
  * @property parent the parent of this context.
  * @property numberImplementation the implementation for numbers of this context.
- * @property reducer the reducer used by this context.
+ * @property abacus the abacus instance used by this reducer.
  */
-open class EvaluationContext(val parent: EvaluationContext? = null,
-                             open val numberImplementation: NumberImplementation? = null,
-                             open val reducer: Reducer<NumberInterface>? = null) {
+abstract class EvaluationContext(val parent: EvaluationContext? = null,
+                                 open val numberImplementation: NumberImplementation? = null,
+                                 open val abacus: Abacus? = null): Reducer<NumberInterface> {
 
     /**
      * The map of variables in this context.
@@ -47,10 +48,10 @@ open class EvaluationContext(val parent: EvaluationContext? = null,
             by ChainSearchDelegate { numberImplementation }
 
     /**
-     * The reducer inherited from this context's parent.
+     * The Abacus instance inherited from this context's parent.
      */
-    val inheritedReducer: Reducer<NumberInterface>
-            by ChainSearchDelegate { reducer }
+    val inheritedAbacus: Abacus
+            by ChainSearchDelegate { abacus }
 
     /**
      * The set of all variables in this context and its parents.

core/src/main/kotlin/org/nwapw/abacus/context/MutableEvaluationContext.kt

@@ -1,23 +1,26 @@
 package org.nwapw.abacus.context
 
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.exception.NumberReducerException
+import org.nwapw.abacus.exception.ReductionException
 import org.nwapw.abacus.number.NumberInterface
 import org.nwapw.abacus.plugin.NumberImplementation
-import org.nwapw.abacus.tree.Reducer
-import org.nwapw.abacus.tree.nodes.TreeNode
+import org.nwapw.abacus.tree.nodes.*
 
 /**
  * A reduction context that is mutable.
+ *
  * @param parent the parent of this context.
  * @param numberImplementation the number implementation used in this context.
- * @param reducer the reducer used in this context
+ * @param abacus the abacus instance used.
  */
 class MutableEvaluationContext(parent: EvaluationContext? = null,
                                numberImplementation: NumberImplementation? = null,
-                               reducer: Reducer<NumberInterface>? = null) :
-        EvaluationContext(parent, numberImplementation, reducer) {
+                               abacus: Abacus? = null) :
+        PluginEvaluationContext(parent, numberImplementation, abacus) {
 
     override var numberImplementation: NumberImplementation? = super.numberImplementation
-    override var reducer: Reducer<NumberInterface>? = super.reducer
+    override var abacus: Abacus? = super.abacus
 
     /**
      * Writes data stored in the [other] context over data stored in this one.
@@ -25,7 +28,6 @@ class MutableEvaluationContext(parent: EvaluationContext? = null,
      */
     fun apply(other: EvaluationContext) {
         if(other.numberImplementation != null) numberImplementation = other.numberImplementation
-        if(other.reducer != null) reducer = other.reducer
         for(name in other.variables) {
             setVariable(name, other.getVariable(name) ?: continue)
         }
@@ -34,36 +36,56 @@ class MutableEvaluationContext(parent: EvaluationContext? = null,
         }
     }
 
-    /**
-     * Sets a variable to a certain [value].
-     * @param name the name of the variable.
-     * @param value the value of the variable.
-     */
-    fun setVariable(name: String, value: NumberInterface) {
-        variableMap[name] = value
-    }
-
-    /**
-     * Set a definition to a certain [value].
-     * @param name the name of the definition.
-     * @param value the value of the definition.
-     */
-    fun setDefinition(name: String, value: TreeNode) {
-        definitionMap[name] = value
-    }
-
-    /**
-     * Clears the variables defined in this context.
-     */
-    fun clearVariables(){
-        variableMap.clear()
-    }
-
-    /**
-     * Clears the definitions defined in this context.
-     */
-    fun clearDefinitions(){
-        definitionMap.clear()
+    override fun reduceNode(treeNode: TreeNode, vararg children: Any): NumberInterface {
+        val oldNumberImplementation = numberImplementation
+        val abacus = inheritedAbacus
+        val promotionManager = abacus.promotionManager
+        val toReturn = when(treeNode){
+            is NumberNode -> {
+                inheritedNumberImplementation.instanceForString(treeNode.number)
+            }
+            is VariableNode -> {
+                val variable = getVariable(treeNode.variable)
+                if(variable != null) return variable
+                val definition = getDefinition(treeNode.variable)
+                if(definition != null) return definition.reduce(this)
+                throw NumberReducerException("variable is not defined.")
+            }
+            is NumberUnaryNode -> {
+                val child = children[0] as NumberInterface
+                numberImplementation = abacus.pluginManager.interfaceImplementationFor(child.javaClass)
+                abacus.pluginManager.operatorFor(treeNode.operation)
+                        .apply(this, child)
+            }
+            is NumberBinaryNode -> {
+                val left = children[0] as NumberInterface
+                val right = children[1] as NumberInterface
+                val promotionResult = promotionManager.promote(left, right)
+                numberImplementation = promotionResult.promotedTo
+                abacus.pluginManager.operatorFor(treeNode.operation).apply(this, *promotionResult.items)
+            }
+            is NumberFunctionNode -> {
+                val promotionResult = promotionManager
+                        .promote(*children.map { it as NumberInterface }.toTypedArray())
+                numberImplementation = promotionResult.promotedTo
+                abacus.pluginManager.functionFor(treeNode.callTo).apply(this, *promotionResult.items)
+            }
+            is TreeValueUnaryNode -> {
+                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
+                        .apply(this, treeNode.applyTo)
+            }
+            is TreeValueBinaryNode -> {
+                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
+                        .apply(this, treeNode.left, treeNode.right)
+            }
+            is TreeValueFunctionNode -> {
+                abacus.pluginManager.treeValueFunctionFor(treeNode.callTo)
+                        .apply(this, *treeNode.children.toTypedArray())
+            }
+            else -> throw ReductionException("unrecognized tree node.")
+        }
+        numberImplementation = oldNumberImplementation
+        return toReturn
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/context/PluginEvaluationContext.kt

@@ -0,0 +1,58 @@
+package org.nwapw.abacus.context
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.tree.nodes.TreeNode
+
+/**
+ * An evaluation context with limited mutability.
+ *
+ * An evaluation context that is mutable but in a limited way, that is, not allowing the modifications
+ * of variables whose changes might cause issues outside of the function. An example of this would be
+ * the modification of the [numberImplementation], which would cause code paths such as the parsing
+ * of NumberNodes to produce a different type of number than if the function did not run, whcih is unacceptable.
+ *
+ * @param parent the parent of this context.
+ * @param numberImplementation the number implementation used in this context.
+ * @param abacus the abacus instance used.
+ */
+abstract class PluginEvaluationContext(parent: EvaluationContext? = null,
+                                       numberImplementation: NumberImplementation? = null,
+                                       abacus: Abacus? = null) :
+        EvaluationContext(parent, numberImplementation, abacus) {
+
+    /**
+     * Sets a variable to a certain [value].
+     * @param name the name of the variable.
+     * @param value the value of the variable.
+     */
+    fun setVariable(name: String, value: NumberInterface) {
+        variableMap[name] = value
+    }
+
+    /**
+     * Set a definition to a certain [value].
+     * @param name the name of the definition.
+     * @param value the value of the definition.
+     */
+    fun setDefinition(name: String, value: TreeNode) {
+        definitionMap[name] = value
+    }
+
+    /**
+     * Clears the variables defined in this context.
+     */
+    fun clearVariables(){
+        variableMap.clear()
+    }
+
+    /**
+     * Clears the definitions defined in this context.
+     */
+    fun clearDefinitions(){
+        definitionMap.clear()
+    }
+
+
+}

core/src/main/kotlin/org/nwapw/abacus/function/Applicable.kt

@@ -1,6 +1,7 @@
 package org.nwapw.abacus.function
 
 import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.exception.DomainException
 
 /**
@@ -18,7 +19,7 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameter array to verify for compatibility.
      * @return whether the array can be used with applyInternal.
      */
-    fun matchesParams(context: MutableEvaluationContext, params: Array<out T>): Boolean
+    fun matchesParams(context: PluginEvaluationContext, params: Array<out T>): Boolean
 
     /**
      * Applies the applicable object to the given parameters,
@@ -26,7 +27,7 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameters to apply to.
      * @return the result of the application.
      */
-    fun applyInternal(context: MutableEvaluationContext, params: Array<out T>): O
+    fun applyInternal(context: PluginEvaluationContext, params: Array<out T>): O
 
     /**
      * If the parameters can be used with this applicable, returns
@@ -35,7 +36,7 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameters to apply to.
      * @return the result of the operation, or null if parameters do not match.
      */
-    fun apply(context: MutableEvaluationContext, vararg params: T): O {
+    fun apply(context: PluginEvaluationContext, vararg params: T): O {
         if (!matchesParams(context, params))
             throw DomainException("parameters do not match function requirements.")
         return applyInternal(context, params)

core/src/main/kotlin/org/nwapw/abacus/number/NumberInterface.kt

@@ -221,6 +221,13 @@ abstract class NumberInterface: Comparable<NumberInterface> {
         return fractionalPartInternal()
     }
 
+    /**
+     * Checks whether the given number is an integer or not.
+     *
+     * @return whether the number is an integer or not.
+     */
+    fun isInteger() = fractionalPart().signum() == 0
+
     /**
      * Returns a NumberRangeBuilder object, which is used to create a range.
      * The reason that this returns a builder and not an actual range is that

core/src/main/kotlin/org/nwapw/abacus/number/promotion/NumberUtils.kt

@@ -3,7 +3,6 @@ package org.nwapw.abacus.number.promotion
 
 import org.nwapw.abacus.number.NumberInterface
 
-typealias PromotionFunction = java.util.function.Function<NumberInterface, NumberInterface>
 typealias PromotionPath = List<PromotionFunction>
 typealias NumberClass = Class<NumberInterface>
 
@@ -14,5 +13,5 @@ typealias NumberClass = Class<NumberInterface>
  * @param from the number to start from.
  */
 fun PromotionPath.promote(from: NumberInterface): NumberInterface {
-    return fold(from, { current, function -> function.apply(current) })
+    return fold(from, { current, function -> function.promote(current) })
 }

core/src/main/kotlin/org/nwapw/abacus/number/promotion/PromotionFunction.kt

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.number.promotion
+
+import org.nwapw.abacus.number.NumberInterface
+
+/**
+ * Function that is used to promote a number from one type to another.
+ *
+ * A promotion function is used in the promotion system as a mean to
+ * actually "travel" down the promotion path.
+ */
+interface PromotionFunction {
+
+    /**
+     * Promotes the given [number] into another type.
+     * @param number the number to promote from.
+     * @return the new number with the same value.
+     */
+    fun promote(number: NumberInterface): NumberInterface
+
+}

core/src/main/kotlin/org/nwapw/abacus/number/promotion/PromotionManager.kt

@@ -6,7 +6,6 @@ import org.nwapw.abacus.number.NumberInterface
 import org.nwapw.abacus.plugin.NumberImplementation
 import org.nwapw.abacus.plugin.PluginListener
 import org.nwapw.abacus.plugin.PluginManager
-import java.util.function.Function
 
 /**
  * A class that handles promotions based on priority and the
@@ -32,7 +31,11 @@ class PromotionManager(val abacus: Abacus) : PluginListener {
         val fromName = abacus.pluginManager.interfaceImplementationNameFor(from.implementation)
         val toName = abacus.pluginManager.interfaceImplementationNameFor(to.implementation)
 
-        if(fromName == toName) return listOf(Function { it })
+        if(fromName == toName) return listOf(object : PromotionFunction {
+            override fun promote(number: NumberInterface): NumberInterface {
+                return number
+            }
+        })
 
         if(from.promotionPaths.containsKey(toName))
             return listOf(from.promotionPaths[toName] ?: return null)

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorAdd.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -11,11 +11,11 @@ import org.nwapw.abacus.number.NumberInterface
  *
  * This is a standard operator that simply performs addition.
  */
-class OperatorAdd: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+class OperatorAdd: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params.size == 2
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params[0] + params[1]
 
 }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorCaret.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 import org.nwapw.abacus.plugin.standard.StandardPlugin.*
 
@@ -12,21 +12,21 @@ import org.nwapw.abacus.plugin.standard.StandardPlugin.*
  *
  * This is a standard operator that brings one number to the power of the other.
  */
-class OperatorCaret: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 2) {
+class OperatorCaret: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 3) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params.size == 2
                     && !(params[0].signum() == 0 && params[1].signum() == 0)
-                    && !(params[0].signum() == -1 && params[1].fractionalPart().signum() != 0)
+                    && !(params[0].signum() == -1 && !params[1].isInteger())
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
         val implementation = context.inheritedNumberImplementation
         if (params[0].signum() == 0)
             return implementation.instanceForString("0")
         else if (params[1].signum() == 0)
             return implementation.instanceForString("1")
         //Detect integer bases:
-        if (params[0].fractionalPart().signum() == 0
+        if (params[0].isInteger()
                 && FUNCTION_ABS.apply(context, params[1]) < implementation.instanceForString(Integer.toString(Integer.MAX_VALUE))
                 && FUNCTION_ABS.apply(context, params[1]) >= implementation.instanceForString("1")) {
             val newParams = arrayOf(params[0], params[1].fractionalPart())

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorDefine.kt

@@ -1,6 +1,6 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
 import org.nwapw.abacus.function.interfaces.TreeValueOperator
@@ -16,13 +16,13 @@ import org.nwapw.abacus.tree.nodes.VariableNode
  */
 class OperatorDefine: TreeValueOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out TreeNode>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out TreeNode>) =
             params.size == 2 && params[0] is VariableNode
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out TreeNode>): NumberInterface {
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out TreeNode>): NumberInterface {
         val assignTo = (params[0] as VariableNode).variable
         context.setDefinition(assignTo, params[1])
-        return params[1].reduce(context.inheritedReducer)
+        return params[1].reduce(context)
     }
 
 }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorDivide.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -11,11 +11,11 @@ import org.nwapw.abacus.number.NumberInterface
  *
  * This is a standard operator that simply performs division.
  */
-class OperatorDivide: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
+class OperatorDivide: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 2) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params.size == 2
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params[0] / params[1]
 
 }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorFactorial.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -13,12 +13,12 @@ import org.nwapw.abacus.number.NumberInterface
  */
 class OperatorFactorial: NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_POSTFIX, 0) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
         params.size == 1
-                && params[0].fractionalPart().signum() == 0
+                && params[0].isInteger()
                 && params[0].signum() >= 0
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
         val implementation = context.inheritedNumberImplementation
         val one = implementation.instanceForString("1")
         if (params[0].signum() == 0) {

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorMultiply.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -11,11 +11,11 @@ import org.nwapw.abacus.number.NumberInterface
  *
  * This is a standard operator that simply performs multiplication.
  */
-class OperatorMultiply: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
+class OperatorMultiply: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 2) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params.size == 2
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params[0] * params[1]
 
 }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorNcr.kt

@@ -1,11 +1,12 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
-import org.nwapw.abacus.plugin.standard.StandardPlugin.*
+import org.nwapw.abacus.plugin.standard.StandardPlugin.OP_FACTORIAL
+import org.nwapw.abacus.plugin.standard.StandardPlugin.OP_NPR
 
 /**
  * The "N choose R" operator.
@@ -13,13 +14,13 @@ import org.nwapw.abacus.plugin.standard.StandardPlugin.*
  * This is a standard operator that returns the number of possible combinations, regardless of order,
  * of a certain size can be taken out of a pool of a bigger size.
  */
-class OperatorNcr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0) {
+class OperatorNcr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 1) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
-            params.size == 2 && params[0].fractionalPart().signum() == 0
-                    && params[1].fractionalPart().signum() == 0
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2 && params[0].isInteger()
+                    && params[1].isInteger()
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             OP_NPR.apply(context, *params) / OP_FACTORIAL.apply(context, params[1])
 
 }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorNegate.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -11,12 +11,12 @@ import org.nwapw.abacus.number.NumberInterface
  *
  * This is a standard operator that negates a number.
  */
-class OperatorNegate: NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_PREFIX, 0) {
+class OperatorNegate: NumberOperator(OperatorAssociativity.LEFT, OperatorType.UNARY_PREFIX, 1) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params.size == 1
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             -params[0]
 
 }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorNpr.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -12,13 +12,13 @@ import org.nwapw.abacus.number.NumberInterface
  * his is a standard operator that returns the number of possible combinations
  * of a certain size can be taken out of a pool of a bigger size.
  */
-class OperatorNpr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 0) {
+class OperatorNpr: NumberOperator(OperatorAssociativity.RIGHT, OperatorType.BINARY_INFIX, 1) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
-            params.size == 2 && params[0].fractionalPart().signum() == 0
-                    && params[1].fractionalPart().signum() == 0
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
+            params.size == 2 && params[0].isInteger()
+                    && params[1].isInteger()
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>): NumberInterface {
         val implementation = context.inheritedNumberImplementation
         if (params[0] < params[1] ||
                 params[0].signum() < 0 ||

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorSet.kt

@@ -1,6 +1,6 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
 import org.nwapw.abacus.function.interfaces.TreeValueOperator
@@ -15,12 +15,12 @@ import org.nwapw.abacus.tree.nodes.VariableNode
  */
 class OperatorSet: TreeValueOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out TreeNode>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out TreeNode>) =
             params.size == 2 && params[0] is VariableNode
 
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out TreeNode>): NumberInterface {
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out TreeNode>): NumberInterface {
         val assignTo = (params[0] as VariableNode).variable
-        val value = params[1].reduce(context.inheritedReducer)
+        val value = params[1].reduce(context)
         context.setVariable(assignTo, value)
         return value
     }

core/src/main/kotlin/org/nwapw/abacus/plugin/standard/operator/OperatorSubtract.kt

@@ -1,9 +1,9 @@
 package org.nwapw.abacus.plugin.standard.operator
 
-import org.nwapw.abacus.context.MutableEvaluationContext
-import org.nwapw.abacus.function.interfaces.NumberOperator
+import org.nwapw.abacus.context.PluginEvaluationContext
 import org.nwapw.abacus.function.OperatorAssociativity
 import org.nwapw.abacus.function.OperatorType
+import org.nwapw.abacus.function.interfaces.NumberOperator
 import org.nwapw.abacus.number.NumberInterface
 
 /**
@@ -11,11 +11,11 @@ import org.nwapw.abacus.number.NumberInterface
  *
  * This is a standard operator that performs subtraction.
  */
-class OperatorSubtract: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+class OperatorSubtract: NumberOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 1) {
 
-    override fun matchesParams(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun matchesParams(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params.size == 2
-    override fun applyInternal(context: MutableEvaluationContext, params: Array<out NumberInterface>) =
+    override fun applyInternal(context: PluginEvaluationContext, params: Array<out NumberInterface>) =
             params[0] - params[1]
 
 }

core/src/main/kotlin/org/nwapw/abacus/tree/standard/NumberReducer.kt

@@ -1,67 +0,0 @@
-package org.nwapw.abacus.tree.standard
-
-import org.nwapw.abacus.Abacus
-import org.nwapw.abacus.context.EvaluationContext
-import org.nwapw.abacus.exception.NumberReducerException
-import org.nwapw.abacus.exception.ReductionException
-import org.nwapw.abacus.number.NumberInterface
-import org.nwapw.abacus.tree.Reducer
-import org.nwapw.abacus.tree.nodes.*
-
-class NumberReducer(val abacus: Abacus, context: EvaluationContext) : Reducer<NumberInterface> {
-
-    val context = context.mutableSubInstance()
-
-    init {
-        this.context.reducer = this
-    }
-
-    override fun reduceNode(treeNode: TreeNode, vararg children: Any): NumberInterface {
-        val promotionManager = abacus.promotionManager
-        return when(treeNode){
-            is NumberNode -> {
-                context.inheritedNumberImplementation.instanceForString(treeNode.number)
-            }
-            is VariableNode -> {
-                val variable = context.getVariable(treeNode.variable)
-                if(variable != null) return variable
-                val definition = context.getDefinition(treeNode.variable)
-                if(definition != null) return definition.reduce(this)
-                throw NumberReducerException("variable is not defined.")
-            }
-            is NumberUnaryNode -> {
-                val child = children[0] as NumberInterface
-                context.numberImplementation = abacus.pluginManager.interfaceImplementationFor(child.javaClass)
-                abacus.pluginManager.operatorFor(treeNode.operation)
-                        .apply(context, child)
-            }
-            is NumberBinaryNode -> {
-                val left = children[0] as NumberInterface
-                val right = children[1] as NumberInterface
-                val promotionResult = promotionManager.promote(left, right)
-                context.numberImplementation = promotionResult.promotedTo
-                abacus.pluginManager.operatorFor(treeNode.operation).apply(context, *promotionResult.items)
-            }
-            is NumberFunctionNode -> {
-                val promotionResult = promotionManager
-                        .promote(*children.map { it as NumberInterface }.toTypedArray())
-                context.numberImplementation = promotionResult.promotedTo
-                abacus.pluginManager.functionFor(treeNode.callTo).apply(context, *promotionResult.items)
-            }
-            is TreeValueUnaryNode -> {
-                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
-                        .apply(context, treeNode.applyTo)
-            }
-            is TreeValueBinaryNode -> {
-                abacus.pluginManager.treeValueOperatorFor(treeNode.operation)
-                        .apply(context, treeNode.left, treeNode.right)
-            }
-            is TreeValueFunctionNode -> {
-                abacus.pluginManager.treeValueFunctionFor(treeNode.callTo)
-                        .apply(context, *treeNode.children.toTypedArray())
-            }
-            else -> throw ReductionException("unrecognized tree node.")
-        }
-    }
-
-}

core/src/test/java/org/nwapw/abacus/tests/RangeTests.java

@@ -5,19 +5,17 @@ import org.junit.BeforeClass;
 import org.junit.Test;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
-import org.nwapw.abacus.number.standard.NaiveNumber;
-import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.number.promotion.PromotionFunction;
 import org.nwapw.abacus.number.range.NumberRange;
+import org.nwapw.abacus.number.standard.NaiveNumber;
 import org.nwapw.abacus.number.standard.PreciseNumber;
 import org.nwapw.abacus.plugin.standard.StandardPlugin;
 
-import java.util.function.Function;
-
 public class RangeTests {
 
     private static Abacus abacus = new Abacus(new Configuration( "precise", new String[]{}));
-    private static Function<NumberInterface, NumberInterface> naivePromotion = i -> new NaiveNumber((i.toString()));
-    private static Function<NumberInterface, NumberInterface> precisePromotion = i -> new PreciseNumber((i.toString()));
+    private static PromotionFunction naivePromotion = i -> new NaiveNumber((i.toString()));
+    private static PromotionFunction precisePromotion = i -> new PreciseNumber((i.toString()));
 
     @BeforeClass
     public static void prepareTests() {

core/src/test/java/org/nwapw/abacus/tests/TokenizerTests.java

@@ -1,19 +1,22 @@
 package org.nwapw.abacus.tests;
 
+import org.jetbrains.annotations.NotNull;
 import org.junit.Assert;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
 import org.nwapw.abacus.context.MutableEvaluationContext;
-import org.nwapw.abacus.function.*;
+import org.nwapw.abacus.context.PluginEvaluationContext;
+import org.nwapw.abacus.function.OperatorAssociativity;
+import org.nwapw.abacus.function.OperatorType;
 import org.nwapw.abacus.function.interfaces.NumberFunction;
 import org.nwapw.abacus.function.interfaces.NumberOperator;
 import org.nwapw.abacus.lexing.Match;
 import org.nwapw.abacus.number.NumberInterface;
 import org.nwapw.abacus.parsing.standard.LexerTokenizer;
-import org.nwapw.abacus.plugin.Plugin;
 import org.nwapw.abacus.parsing.standard.TokenType;
+import org.nwapw.abacus.plugin.Plugin;
 
 import java.util.List;
 
@@ -23,12 +26,12 @@ public class TokenizerTests {
     private static LexerTokenizer lexerTokenizer = new LexerTokenizer();
     private static NumberFunction subtractFunction = new NumberFunction() {
         @Override
-        public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+        public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
             return params.length == 2;
         }
 
         @Override
-        public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+        public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
             return params[0].subtract(params[1]);
         }
     };
@@ -39,12 +42,12 @@ public class TokenizerTests {
                     0) {
 
                 @Override
-                public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+                public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
                     return true;
                 }
 
-                                @Override
-                public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+                @Override
+                public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
                     return subtractFunction.apply(context, params);
                 }
             });
@@ -52,12 +55,12 @@ public class TokenizerTests {
                     0) {
 
                 @Override
-                public boolean matchesParams(MutableEvaluationContext context, NumberInterface[] params) {
+                public boolean matchesParams(PluginEvaluationContext context, NumberInterface[] params) {
                     return true;
                 }
 
-                                @Override
-                public NumberInterface applyInternal(MutableEvaluationContext context, NumberInterface[] params) {
+                @Override
+                public NumberInterface applyInternal(PluginEvaluationContext context, NumberInterface[] params) {
                     return subtractFunction.apply(context, params);
                 }
             });

fx/src/main/java/org/nwapw/abacus/fx/AbacusApplication.java

@@ -26,7 +26,7 @@ public class AbacusApplication extends Application {
         FXMLLoader loader = new FXMLLoader(getClass().getResource("/abacus.fxml"));
         Parent parent = loader.load();
         controller = loader.getController();
-        Scene mainScene = new Scene(parent, 320, 480);
+        Scene mainScene = new Scene(parent, 420, 520);
         primaryStage.setScene(mainScene);
         primaryStage.setTitle("Abacus");
         primaryStage.show();

fx/src/main/java/org/nwapw/abacus/fx/AbacusController.java

@@ -8,6 +8,7 @@ import javafx.fxml.FXML;
 import javafx.scene.control.*;
 import javafx.scene.control.cell.CheckBoxListCell;
 import javafx.scene.text.Text;
+import javafx.stage.FileChooser;
 import javafx.util.Callback;
 import javafx.util.StringConverter;
 import org.nwapw.abacus.Abacus;
@@ -16,7 +17,6 @@ import org.nwapw.abacus.exception.AbacusException;
 import org.nwapw.abacus.function.Documentation;
 import org.nwapw.abacus.function.DocumentationType;
 import org.nwapw.abacus.number.*;
-import org.nwapw.abacus.plugin.ClassFinder;
 import org.nwapw.abacus.plugin.PluginListener;
 import org.nwapw.abacus.plugin.PluginManager;
 import org.nwapw.abacus.plugin.standard.StandardPlugin;
@@ -24,9 +24,12 @@ import org.nwapw.abacus.EvaluationResult;
 import org.nwapw.abacus.tree.nodes.TreeNode;
 
 import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Comparator;
+import java.util.Scanner;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -70,6 +73,7 @@ public class AbacusController implements PluginListener {
      * Constant string that is displayed if the calculations are interrupted by an exception.
      */
     private static final String ERR_EXCEPTION = "Exception Thrown";
+    private static final String ERR_DEFINITION = "Definition Error";
     @FXML
     private TabPane coreTabPane;
     @FXML
@@ -104,6 +108,8 @@ public class AbacusController implements PluginListener {
     private ListView<Documentation> functionListView;
     @FXML
     private TextField functionListSearchField;
+    @FXML
+    private ListView<String> definitionFilesView;
 
     /**
      * The list of history entries, created by the users.
@@ -129,6 +135,10 @@ public class AbacusController implements PluginListener {
      * The filtered list displayed to the user.
      */
     private FilteredList<Documentation> functionFilter;
+    /**
+     * The list of definition files to be loaded.
+     */
+    private ObservableList<String> definitionFiles;
 
     /**
      * The abacus instance used for changing the plugin configuration.
@@ -252,6 +262,9 @@ public class AbacusController implements PluginListener {
             if (oldValue.equals(settingsTab)) alertIfApplyNeeded(true);
         });
 
+        definitionFiles = FXCollections.observableArrayList();
+        definitionFilesView.setItems(definitionFiles);
+
         abacus = new Abacus(new ExtendedConfiguration(CONFIG_FILE));
         PluginManager abacusPluginManager = abacus.getPluginManager();
         abacusPluginManager.addListener(this);
@@ -305,6 +318,25 @@ public class AbacusController implements PluginListener {
         reloadAlertShown = false;
     }
 
+    private void loadDefinitionFile(String fileName){
+        File definitionFile = new File(fileName);
+        if(!definitionFile.exists()) return;
+        try {
+            FileReader fileReader = new FileReader(definitionFile);
+            Scanner scanner = new Scanner(fileReader);
+            while(scanner.hasNext()){
+                EvaluationResult result = abacus.evaluateTree(abacus.parseString(scanner.nextLine()));
+                abacus.applyToContext(result.getResultingContext());
+            }
+        } catch (AbacusException abacusError) {
+            outputText.setText(ERR_DEFINITION + " (" + abacusError.getMessage() + ")");
+            abacusError.printStackTrace();
+        } catch (RuntimeException runtime) {
+            outputText.setText(ERR_DEFINITION + " (" + ERR_EXCEPTION + ")");
+            runtime.printStackTrace();
+        } catch (FileNotFoundException ignored) {}
+    }
+
     @FXML
     public void performScan() {
         PluginManager abacusPluginManager = abacus.getPluginManager();
@@ -315,34 +347,62 @@ public class AbacusController implements PluginListener {
         } catch (IOException | ClassNotFoundException e) {
             e.printStackTrace();
         }
-        abacus.reload();
+        reloadAbacus();
     }
 
     @FXML
     public void performReload() {
         alertIfApplyNeeded(true);
-        abacus.reload();
+        reloadAbacus();
     }
 
     @FXML
     public void performSave() {
-        Configuration configuration = abacus.getConfiguration();
+        ExtendedConfiguration configuration = (ExtendedConfiguration) abacus.getConfiguration();
         configuration.setNumberImplementation(numberImplementationBox.getSelectionModel().getSelectedItem());
         Set<String> disabledPlugins = configuration.getDisabledPlugins();
         disabledPlugins.clear();
         for (ToggleablePlugin pluginEntry : enabledPlugins) {
             if (!pluginEntry.isEnabled()) disabledPlugins.add(pluginEntry.getClassName());
         }
+        Set<String> abacusDefinitionFiles = configuration.getDefinitionFiles();
+        abacusDefinitionFiles.clear();
+        abacusDefinitionFiles.addAll(definitionFiles);
         if (computationLimitField.getText().matches("\\d*(\\.\\d+)?") && computationLimitField.getText().length() != 0)
-            ((ExtendedConfiguration) configuration).setComputationDelay(Double.parseDouble(computationLimitField.getText()));
-        ((ExtendedConfiguration) configuration).saveTo(CONFIG_FILE);
+            configuration.setComputationDelay(Double.parseDouble(computationLimitField.getText()));
+        configuration.saveTo(CONFIG_FILE);
         changesMade = false;
         reloadAlertShown = false;
     }
 
+    @FXML
+    public void performAddDefinitionFile(){
+        FileChooser fileChooser = new FileChooser();
+        fileChooser.setTitle("Add definition file");
+        File selectedFile = fileChooser.showOpenDialog(null);
+        if(selectedFile == null) return;
+        String absolutePath = selectedFile.getAbsolutePath();
+        if(!definitionFiles.contains(absolutePath)) definitionFiles.add(absolutePath);
+        changesMade = true;
+    }
+
+    @FXML
+    public void performRemoveDefinitionFile(){
+        String selectedItem = definitionFilesView.getSelectionModel().getSelectedItem();
+        if(selectedItem != null) definitionFiles.remove(selectedItem);
+        changesMade = true;
+    }
+
+    private void reloadAbacus(){
+        abacus.reload();
+        for(String file : definitionFiles){
+            loadDefinitionFile(file);
+        }
+    }
+
     @Override
     public void onLoad(PluginManager manager) {
-        Configuration configuration = abacus.getConfiguration();
+        ExtendedConfiguration configuration = (ExtendedConfiguration) abacus.getConfiguration();
         Set<String> disabledPlugins = configuration.getDisabledPlugins();
         numberImplementationOptions.addAll(abacus.getPluginManager().getAllNumberImplementations());
         String actualImplementation = configuration.getNumberImplementation();
@@ -360,11 +420,15 @@ public class AbacusController implements PluginListener {
             if(documentationInstance == null)
                 documentationInstance = new Documentation(name, "", "", "", DocumentationType.FUNCTION);
             return documentationInstance;
-        })
-                .collect(Collectors.toCollection(ArrayList::new)));
-        functionList.addAll(manager.getAllTreeValueFunctions().stream().map(name -> pluginManager.documentationFor(name, DocumentationType.TREE_VALUE_FUNCTION))
-                .collect(Collectors.toCollection(ArrayList::new)));
+        }).collect(Collectors.toCollection(ArrayList::new)));
+        functionList.addAll(manager.getAllTreeValueFunctions().stream().map(name -> {
+            Documentation documentationInstance = pluginManager.documentationFor(name, DocumentationType.TREE_VALUE_FUNCTION);
+            if(documentationInstance == null)
+                documentationInstance = new Documentation(name, "", "", "", DocumentationType.TREE_VALUE_FUNCTION);
+            return documentationInstance;
+        }).collect(Collectors.toCollection(ArrayList::new)));
         functionList.sort(Comparator.comparing(Documentation::getCodeName));
+        definitionFiles.addAll(configuration.getDefinitionFiles());
     }
 
     @Override
@@ -372,6 +436,7 @@ public class AbacusController implements PluginListener {
         functionList.clear();
         enabledPlugins.clear();
         numberImplementationOptions.clear();
+        definitionFiles.clear();
     }
 
 }

fx/src/main/java/org/nwapw/abacus/fx/ClassFinder.java

@@ -1,4 +1,4 @@
-package org.nwapw.abacus.plugin;
+package org.nwapw.abacus.fx;
 
 import java.io.File;
 import java.io.IOException;

fx/src/main/kotlin/org/nwapw/abacus/fx/ExtendedConfiguration.kt

@@ -17,8 +17,9 @@ import java.io.File
  * @param disabledPlugins the list of plugins that should be disabled, same as [Configuration.disabledPlugins]
  */
 class ExtendedConfiguration(var computationDelay: Double = 0.0,
-                     implementation: String = "<default>",
-                     disabledPlugins: Array<String> = emptyArray())
+                            definitionFiles: Array<String> = emptyArray(),
+                            implementation: String = "<default>",
+                            disabledPlugins: Array<String> = emptyArray())
     : Configuration(implementation, disabledPlugins) {
 
     companion object {
@@ -27,6 +28,7 @@ class ExtendedConfiguration(var computationDelay: Double = 0.0,
          */
         val DEFAULT_TOML_STRING = """
             computationDelay=0.0
+            definitionFiles=[]
             implementation="naive"
             disabledPlugins=[]
             """
@@ -40,6 +42,11 @@ class ExtendedConfiguration(var computationDelay: Double = 0.0,
         val DEFAULT_TOML_WRITER = TomlWriter()
     }
 
+    /**
+     * The set of files that definitions should be loaded from.
+     */
+    val definitionFiles: MutableSet<String> = mutableSetOf(*definitionFiles)
+
     /**
      * Constructs a new configuration from a file on disk.
      * @param tomlFile the file from disk to load.
@@ -59,6 +66,8 @@ class ExtendedConfiguration(var computationDelay: Double = 0.0,
         numberImplementation = config.numberImplementation
         disabledPlugins.clear()
         disabledPlugins.addAll(config.disabledPlugins)
+        definitionFiles.clear()
+        definitionFiles.addAll(config.definitionFiles)
     }
 
     /**

fx/src/main/resources/abacus.fxml

@@ -47,17 +47,33 @@
                     </padding>
                     <Label text="Number Implementation" GridPane.columnIndex="0" GridPane.rowIndex="0"/>
                     <ComboBox fx:id="numberImplementationBox" GridPane.columnIndex="1" GridPane.rowIndex="0"/>
+
+                    <Label text="Plugins:" GridPane.columnIndex="0" GridPane.rowIndex="1"/>
                     <ListView fx:id="enabledPluginView"
-                              GridPane.rowIndex="1" GridPane.columnIndex="0"
+                              GridPane.rowIndex="2" GridPane.columnIndex="0"
                               GridPane.columnSpan="2" maxHeight="100"/>
-                    <Text GridPane.columnIndex="0" GridPane.rowIndex="2" text="Computation Limit"/>
-                    <TextField fx:id="computationLimitField" GridPane.columnIndex="1" GridPane.rowIndex="2"/>
-                    <FlowPane GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="3" hgap="10"
+
+                    <Label GridPane.columnIndex="0" GridPane.rowIndex="3" text="Computation Limit"/>
+                    <TextField fx:id="computationLimitField" GridPane.columnIndex="1" GridPane.rowIndex="3"/>
+
+                    <Label text="Definition Files:" GridPane.columnIndex="0" GridPane.rowIndex="4"/>
+                    <ListView fx:id="definitionFilesView"
+                              GridPane.columnIndex="0" GridPane.columnSpan="2"
+                              GridPane.rowIndex="5" maxHeight="100"/>
+                    <FlowPane GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="6" hgap="10"
                               vgap="10">
-                        <Button text="Save" onAction="#performSave"/>
-                        <Button text="Reload Plugins" onAction="#performReload"/>
-                        <Button text="Apply and Reload" onAction="#performSaveAndReload"/>
-                        <Button text="Scan Plugins" onAction="#performScan"/>
+                        <Button text="Add" onAction="#performAddDefinitionFile"/>
+                        <Button text="Remove" onAction="#performRemoveDefinitionFile"/>
+                    </FlowPane>
+
+                    <Separator GridPane.rowIndex="7"/>
+
+                    <FlowPane GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="8" hgap="10"
+                              vgap="10">
+                        <Button text="Save Settings" onAction="#performSave"/>
+                        <Button text="Reload Plugins And Definitions" onAction="#performReload"/>
+                        <Button text="Save and Reload" onAction="#performSaveAndReload"/>
+                        <Button text="Reload Plugins From Disk" onAction="#performScan"/>
                     </FlowPane>
                 </GridPane>
             </Tab>