Add comments to the new configuration classes.

Remove the use of null in Applicable calls.

core/build.gradle

@@ -1,4 +1,3 @@
 dependencies {
-    compile 'com.moandjiezana.toml:toml4j:0.7.1'
     testCompile 'junit:junit:4.12'
 }

core/src/main/java/org/nwapw/abacus/Abacus.java

@@ -1,150 +0,0 @@
-package org.nwapw.abacus;
-
-import org.nwapw.abacus.config.Configuration;
-import org.nwapw.abacus.number.NumberInterface;
-import org.nwapw.abacus.number.PromotionManager;
-import org.nwapw.abacus.parsing.LexerTokenizer;
-import org.nwapw.abacus.parsing.ShuntingYardParser;
-import org.nwapw.abacus.parsing.TreeBuilder;
-import org.nwapw.abacus.plugin.NumberImplementation;
-import org.nwapw.abacus.plugin.PluginManager;
-import org.nwapw.abacus.plugin.StandardPlugin;
-import org.nwapw.abacus.tree.NumberReducer;
-import org.nwapw.abacus.tree.TreeNode;
-
-/**
- * The main calculator class. This is responsible
- * for piecing together all of the components, allowing
- * their interaction with each other.
- */
-public class Abacus {
-
-    /**
-     * The default number implementation to be used if no other one is available / selected.
-     */
-    public static final NumberImplementation DEFAULT_IMPLEMENTATION = StandardPlugin.IMPLEMENTATION_NAIVE;
-
-    /**
-     * The plugin manager responsible for
-     * loading and unloading plugins,
-     * and getting functions from them.
-     */
-    private PluginManager pluginManager;
-    /**
-     * The reducer used to evaluate the tree.
-     */
-    private NumberReducer numberReducer;
-    /**
-     * The configuration loaded from a file.
-     */
-    private Configuration configuration;
-    /**
-     * The tree builder used to construct a tree
-     * from a string.
-     */
-    private TreeBuilder treeBuilder;
-    /**
-     * Promotion manager responsible for the promotion system.
-     */
-    private PromotionManager promotionManager;
-
-    /**
-     * Creates a new instance of the Abacus calculator.
-     *
-     * @param configuration the configuration object for this Abacus instance.
-     */
-    public Abacus(Configuration configuration) {
-        pluginManager = new PluginManager(this);
-        numberReducer = new NumberReducer(this);
-        this.configuration = new Configuration(configuration);
-        LexerTokenizer lexerTokenizer = new LexerTokenizer();
-        ShuntingYardParser shuntingYardParser = new ShuntingYardParser();
-        treeBuilder = new TreeBuilder<>(lexerTokenizer, shuntingYardParser);
-        promotionManager = new PromotionManager(this);
-
-        pluginManager.addListener(shuntingYardParser);
-        pluginManager.addListener(lexerTokenizer);
-        pluginManager.addListener(promotionManager);
-    }
-
-    /**
-     * Gets the promotion manager.
-     *
-     * @return the promotion manager.
-     */
-    public PromotionManager getPromotionManager() {
-        return promotionManager;
-    }
-
-    /**
-     * Gets the current tree builder.
-     *
-     * @return the main tree builder in this abacus instance.
-     */
-    public TreeBuilder getTreeBuilder() {
-        return treeBuilder;
-    }
-
-    /**
-     * Gets the current plugin manager,
-     *
-     * @return the plugin manager in this abacus instance.
-     */
-    public PluginManager getPluginManager() {
-        return pluginManager;
-    }
-
-    /**
-     * Get the reducer that is responsible for transforming
-     * an expression into a number.
-     *
-     * @return the number reducer in this abacus instance.
-     */
-    public NumberReducer getNumberReducer() {
-        return numberReducer;
-    }
-
-    /**
-     * Gets the configuration object associated with this instance.
-     *
-     * @return the configuration object.
-     */
-    public Configuration getConfiguration() {
-        return configuration;
-    }
-
-    /**
-     * Parses a string into a tree structure using the main
-     * tree builder.
-     *
-     * @param input the input string to parse
-     * @return the resulting tree, null if the tree builder or the produced tree are null.
-     */
-    public TreeNode parseString(String input) {
-        return treeBuilder.fromString(input);
-    }
-
-    /**
-     * Evaluates the given tree using the main
-     * number reducer.
-     *
-     * @param tree the tree to reduce, must not be null.
-     * @return the resulting number, or null of the reduction failed.
-     */
-    public NumberInterface evaluateTree(TreeNode tree) {
-        return tree.reduce(numberReducer);
-    }
-
-    /**
-     * Gets the number implementation.
-     *
-     * @return the number implementation to use for creating numbers.
-     */
-    public NumberImplementation getNumberImplementation() {
-        NumberImplementation selectedImplementation =
-                pluginManager.numberImplementationFor(configuration.getNumberImplementation());
-        if (selectedImplementation != null) return selectedImplementation;
-        return DEFAULT_IMPLEMENTATION;
-    }
-
-}

core/src/main/java/org/nwapw/abacus/config/Configuration.java

@@ -1,159 +0,0 @@
-package org.nwapw.abacus.config;
-
-import com.moandjiezana.toml.Toml;
-import com.moandjiezana.toml.TomlWriter;
-
-import java.io.File;
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.HashSet;
-import java.util.Set;
-
-/**
- * The configuration object that stores
- * options that the user can change.
- */
-public class Configuration {
-
-    /**
-     * The defaults TOML string.
-     */
-    private static final String DEFAULT_CONFIG =
-            "numberImplementation = \"naive\"\n" +
-                    "disabledPlugins = []";
-    /**
-     * The defaults TOML object, parsed from the string.
-     */
-    private static final Toml DEFAULT_TOML = new Toml().read(DEFAULT_CONFIG);
-    /**
-     * The TOML writer used to write this configuration to a file.
-     */
-    private static final TomlWriter TOML_WRITER = new TomlWriter();
-
-    /**
-     * The computation delay for which the thread can run without interruption.
-     */
-    private double computationDelay = 0;
-    /**
-     * The implementation of the number that should be used.
-     */
-    private String numberImplementation = "<default>";
-    /**
-     * The list of disabled plugins in this Configuration.
-     */
-    private Set<String> disabledPlugins = new HashSet<>();
-
-    /**
-     * Creates a new configuration form the given configuration.
-     *
-     * @param copyFrom the configuration to copy.
-     */
-    public Configuration(Configuration copyFrom) {
-        copyFrom(copyFrom);
-    }
-
-    /**
-     * Creates a new configuration with the given values.
-     *
-     * @param computationDelay     the delay before the computation gets killed.
-     * @param numberImplementation the number implementation, like "naive" or "precise"
-     * @param disabledPlugins      the list of disabled plugins.
-     */
-    public Configuration(double computationDelay, String numberImplementation, String[] disabledPlugins) {
-        this.computationDelay = computationDelay;
-        this.numberImplementation = numberImplementation;
-        this.disabledPlugins.addAll(Arrays.asList(disabledPlugins));
-    }
-
-    /**
-     * Loads a configuration from a given file, keeping non-specified fields default.
-     *
-     * @param fromFile the file to load from.
-     */
-    public Configuration(File fromFile) {
-        if (!fromFile.exists()) return;
-        copyFrom(new Toml(DEFAULT_TOML).read(fromFile).to(Configuration.class));
-    }
-
-    /**
-     * Copies the values from the given configuration into this one.
-     *
-     * @param otherConfiguration the configuration to copy from.
-     */
-    public void copyFrom(Configuration otherConfiguration) {
-        this.computationDelay = otherConfiguration.computationDelay;
-        this.numberImplementation = otherConfiguration.numberImplementation;
-        this.disabledPlugins.addAll(otherConfiguration.disabledPlugins);
-    }
-
-    /**
-     * Saves this configuration to the given file, creating
-     * any directories that do not exist.
-     *
-     * @param file the file to save to.
-     */
-    public void saveTo(File file) {
-        if (file.getParentFile() != null) file.getParentFile().mkdirs();
-        try {
-            TOML_WRITER.write(this, file);
-        } catch (IOException e) {
-            e.printStackTrace();
-        }
-    }
-
-    /**
-     * Gets the value of this configuration as a string.
-     *
-     * @return the string that represents this configuration.
-     */
-    public String asTomlString() {
-        return TOML_WRITER.write(this);
-    }
-
-    /**
-     * Gets the number implementation from this configuration.
-     *
-     * @return the number implementation.
-     */
-    public String getNumberImplementation() {
-        return numberImplementation;
-    }
-
-    /**
-     * Sets the number implementation for the configuration
-     *
-     * @param numberImplementation the number implementation.
-     */
-    public void setNumberImplementation(String numberImplementation) {
-        this.numberImplementation = numberImplementation;
-    }
-
-    /**
-     * Gets the list of disabled plugins.
-     *
-     * @return the list of disabled plugins.
-     */
-    public Set<String> getDisabledPlugins() {
-        return disabledPlugins;
-    }
-
-
-    /**
-     * Gets the computation delay specified in the configuration.
-     *
-     * @return the computaton delay.
-     */
-    public double getComputationDelay() {
-        return computationDelay;
-    }
-
-    /**
-     * Sets the computation delay.
-     *
-     * @param computationDelay the new computation delay.
-     */
-    public void setComputationDelay(double computationDelay) {
-        this.computationDelay = computationDelay;
-    }
-
-}

core/src/main/java/org/nwapw/abacus/function/DomainException.java

@@ -0,0 +1,24 @@
+package org.nwapw.abacus.function;
+
+/**
+ * Exception thrown if the function parameters do not match
+ * requirements.
+ */
+public class DomainException extends RuntimeException {
+
+    /**
+     * Creates a new DomainException.
+     * @param reason the reason for which the exception is thrown.
+     */
+    public DomainException(String reason) {
+        super(reason);
+    }
+
+    /**
+     * Creates a new DomainException with a default message.
+     */
+    public DomainException(){
+        this("Domain Error");
+    }
+
+}

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

@@ -2,6 +2,7 @@ package org.nwapw.abacus.plugin;
 
 import org.nwapw.abacus.function.*;
 import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.variables.VariableDatabase;
 
 /**
  * A plugin class that can be externally implemented and loaded via the
@@ -219,4 +220,12 @@ public abstract class Plugin {
      */
     public abstract void onDisable();
 
+    /**
+     * Get the variable database.
+     * @return the variable database.
+     */
+    public final VariableDatabase getVariableDatabase(){
+        return manager.getVariableDatabase();
+    }
+
 }

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

@@ -3,6 +3,7 @@ package org.nwapw.abacus.plugin;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.function.*;
 import org.nwapw.abacus.number.NumberInterface;
+import org.nwapw.abacus.variables.VariableDatabase;
 
 import java.lang.reflect.InvocationTargetException;
 import java.util.HashMap;
@@ -421,4 +422,12 @@ public class PluginManager {
     public Set<Class<?>> getLoadedPluginClasses() {
         return loadedPluginClasses;
     }
+
+    /**
+     * Gets the variable database.
+     * @return the database.
+     */
+    public VariableDatabase getVariableDatabase(){
+        return abacus.getVariableDatabase();
+    }
 }

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

@@ -1,9 +1,14 @@
 package org.nwapw.abacus.plugin;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.nwapw.abacus.function.*;
 import org.nwapw.abacus.number.NaiveNumber;
 import org.nwapw.abacus.number.NumberInterface;
 import org.nwapw.abacus.number.PreciseNumber;
+import org.nwapw.abacus.tree.Reducer;
+import org.nwapw.abacus.tree.TreeNode;
+import org.nwapw.abacus.tree.VariableNode;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -14,6 +19,40 @@ import java.util.HashMap;
  */
 public class StandardPlugin extends Plugin {
 
+    /**
+     * The set operator.
+     */
+    public final TreeValueOperator opSet = new TreeValueOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+        @Override
+        public boolean matchesParams(NumberImplementation implementation, TreeNode[] params) {
+            return params.length == 2 && params[0] instanceof VariableNode;
+        }
+
+        @Override
+        public NumberInterface applyWithReducerInternal(NumberImplementation implementation, Reducer<? extends NumberInterface> reducer, TreeNode[] params) {
+            String assignTo = ((VariableNode) params[0]).getVariable();
+            NumberInterface value = params[1].reduce(reducer);
+            getVariableDatabase().getVariables().put(assignTo, value);
+            return value;
+        }
+    };
+    /**
+     * The define operator.
+     */
+    public final TreeValueOperator opDefine = new TreeValueOperator(OperatorAssociativity.LEFT, OperatorType.BINARY_INFIX, 0) {
+        @Override
+        public boolean matchesParams(NumberImplementation implementation, TreeNode[] params) {
+            return params.length == 2 && params[0] instanceof VariableNode;
+        }
+
+        @Nullable
+        @Override
+        public NumberInterface applyWithReducerInternal(NumberImplementation implementation, Reducer<? extends NumberInterface> reducer, TreeNode[] params) {
+            String assignTo = ((VariableNode) params[0]).getVariable();
+            getVariableDatabase().getDefinitions().put(assignTo, params[1]);
+            return params[1].reduce(reducer);
+        }
+    };
     /**
      * The addition operator, +
      */
@@ -712,6 +751,9 @@ public class StandardPlugin extends Plugin {
         registerOperator("^", OP_CARET);
         registerOperator("!", OP_FACTORIAL);
 
+        registerTreeValueOperator("=", opSet);
+        registerTreeValueOperator(":=", opDefine);
+
         registerOperator("nPr", OP_NPR);
         registerOperator("nCr", OP_NCR);
 

core/src/main/java/org/nwapw/abacus/tree/NumberReducer.java

@@ -8,6 +8,7 @@ import org.nwapw.abacus.function.TreeValueOperator;
 import org.nwapw.abacus.number.NumberInterface;
 import org.nwapw.abacus.number.PromotionManager;
 import org.nwapw.abacus.number.PromotionResult;
+import org.nwapw.abacus.variables.VariableDatabase;
 
 /**
  * A reducer implementation that turns a tree into a single number.
@@ -35,6 +36,12 @@ public class NumberReducer implements Reducer<NumberInterface> {
         if (node instanceof NumberNode) {
             return abacus.getNumberImplementation().instanceForString(((NumberNode) node).getNumber());
         } else if (node instanceof VariableNode) {
+            VariableDatabase database = abacus.getVariableDatabase();
+            String name = ((VariableNode) node).getVariable();
+            NumberInterface variable = database.getVariables().get(name);
+            if(variable != null) return variable;
+            TreeNode definition = database.getDefinitions().get(name);
+            if(definition != null) return definition.reduce(this);
             return abacus.getNumberImplementation().instanceForString("0");
         } else if (node instanceof NumberBinaryNode) {
             NumberInterface left = (NumberInterface) children[0];

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

@@ -0,0 +1,90 @@
+package org.nwapw.abacus
+
+import org.nwapw.abacus.config.Configuration
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.number.PromotionManager
+import org.nwapw.abacus.parsing.LexerTokenizer
+import org.nwapw.abacus.parsing.ShuntingYardParser
+import org.nwapw.abacus.parsing.TreeBuilder
+import org.nwapw.abacus.plugin.NumberImplementation
+import org.nwapw.abacus.plugin.PluginManager
+import org.nwapw.abacus.plugin.StandardPlugin
+import org.nwapw.abacus.tree.NumberReducer
+import org.nwapw.abacus.tree.TreeNode
+import org.nwapw.abacus.variables.VariableDatabase
+
+/**
+ * Core class to handle all mathematics.
+ *
+ * The main calculator class. This is responsible
+ * for piecing together all of the components, allowing
+ * their interaction with each other.
+ *
+ * @property configuration the configuration to use.
+ */
+class Abacus(val configuration: Configuration) {
+
+    /**
+     * The tokenizer used to convert strings into tokens.
+     */
+    private val tokenizer = LexerTokenizer()
+    /**
+     * Parser the parser used to convert tokens into trees.
+     */
+    private val parser = ShuntingYardParser()
+    /**
+     * The plugin manager used to handle loading and unloading plugins.
+     */
+    val pluginManager = PluginManager(this)
+    /**
+     * The reducer used to turn trees into a single number.
+     */
+    val numberReducer = NumberReducer(this)
+    /**
+     * The tree builder that handles the conversion of strings into trees.
+     */
+    val treeBuilder = TreeBuilder(tokenizer, parser)
+    /**
+     * The promotion manager used to convert between number implementations.
+     */
+    val promotionManager = PromotionManager(this)
+    /**
+     * The database of variable definitions.
+     */
+    val variableDatabase = VariableDatabase(this)
+    /**
+     * The number implementation used by default.
+     */
+    val numberImplementation: NumberImplementation
+        get() {
+            val selectedImplementation =
+                    pluginManager.numberImplementationFor(configuration.numberImplementation)
+            if (selectedImplementation != null) return selectedImplementation
+            return StandardPlugin.IMPLEMENTATION_NAIVE
+        }
+
+    init {
+        pluginManager.addListener(tokenizer)
+        pluginManager.addListener(parser)
+        pluginManager.addListener(promotionManager)
+        pluginManager.addListener(variableDatabase)
+    }
+
+    /**
+     * Parses a string into a tree structure using the main
+     * tree builder.
+     *
+     * @param input the input string to parse
+     * @return the resulting tree, null if the tree builder or the produced tree are null.
+     */
+    fun parseString(input: String): TreeNode? = treeBuilder.fromString(input)
+    /**
+     * Evaluates the given tree using the main
+     * number reducer.
+     *
+     * @param tree the tree to reduce, must not be null.
+     * @return the resulting number, or null of the reduction failed.
+     */
+    fun evaluateTree(tree: TreeNode): NumberInterface? = tree.reduce(numberReducer)
+
+}

core/src/main/kotlin/org/nwapw/abacus/config/Configuration.kt

@@ -0,0 +1,20 @@
+package org.nwapw.abacus.config
+
+/**
+ * A class that holds information that tells Abacus how to behave.
+ *
+ * Configuration stores information about how Abacus should behave, for
+ * instance, what number implementation it should use and what
+ * plugins should be ignored during loading.
+ *
+ * @property numberImplementation the number implementation Abacus should use for loading.
+ * @param disabledPlugins the plugins that should be disabled and not loaded by the plugin manager.
+ */
+open class Configuration(var numberImplementation: String = "<default>", disabledPlugins: Array<String> = emptyArray()) {
+
+    /**
+     * The set of disabled plugins that should be ignored by the plugin manager.
+     */
+    val disabledPlugins = disabledPlugins.toMutableSet()
+
+}

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

@@ -1,5 +1,6 @@
 package org.nwapw.abacus.function.applicable
 
+import org.nwapw.abacus.function.DomainException
 import org.nwapw.abacus.plugin.NumberImplementation
 
 /**
@@ -25,7 +26,7 @@ interface Applicable<in T : Any, out O : Any> {
      * @param params the parameters to apply to.
      * @return the result of the application.
      */
-    fun applyInternal(implementation: NumberImplementation, params: Array<out T>): O?
+    fun applyInternal(implementation: NumberImplementation, params: Array<out T>): O
 
     /**
      * If the parameters can be used with this applicable, returns
@@ -34,8 +35,8 @@ 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(implementation: NumberImplementation, vararg params: T): O? {
-        if (!matchesParams(implementation, params)) return null
+    fun apply(implementation: NumberImplementation, vararg params: T): O {
+        if (!matchesParams(implementation, params)) throw DomainException()
         return applyInternal(implementation, params)
     }
 

core/src/main/kotlin/org/nwapw/abacus/function/applicable/ReducerApplicable.kt

@@ -1,5 +1,6 @@
 package org.nwapw.abacus.function.applicable
 
+import org.nwapw.abacus.function.DomainException
 import org.nwapw.abacus.plugin.NumberImplementation
 import org.nwapw.abacus.tree.Reducer
 
@@ -27,7 +28,7 @@ interface ReducerApplicable<in T : Any, out O : Any, in R : Any> {
      * @param params the arguments to apply to.
      * @return the result of the application.
      */
-    fun applyWithReducerInternal(implementation: NumberImplementation, reducer: Reducer<R>, params: Array<out T>): O?
+    fun applyWithReducerInternal(implementation: NumberImplementation, reducer: Reducer<R>, params: Array<out T>): O
 
     /**
      * Applies this applicable to the given arguments, and reducer,
@@ -36,8 +37,8 @@ interface ReducerApplicable<in T : Any, out O : Any, in R : Any> {
      * @param params the arguments to apply to.
      * @return the result of the application, or null if the arguments are incompatible.
      */
-    fun applyWithReducer(implementation: NumberImplementation, reducer: Reducer<R>, vararg params: T): O? {
-        if (!matchesParams(implementation, params)) return null
+    fun applyWithReducer(implementation: NumberImplementation, reducer: Reducer<R>, vararg params: T): O {
+        if (!matchesParams(implementation, params)) throw DomainException()
         return applyWithReducerInternal(implementation, reducer, params)
     }
 

core/src/main/kotlin/org/nwapw/abacus/variables/VariableDatabase.kt

@@ -0,0 +1,37 @@
+package org.nwapw.abacus.variables
+
+import org.nwapw.abacus.Abacus
+import org.nwapw.abacus.number.NumberInterface
+import org.nwapw.abacus.plugin.PluginListener
+import org.nwapw.abacus.plugin.PluginManager
+import org.nwapw.abacus.tree.TreeNode
+
+/**
+ * A database for variables and definition.
+ *
+ * The variable database is used to keep track of
+ * variables and definitions throughout the calculator.
+ *
+ * @property abacus the Abacus instance.
+ */
+class VariableDatabase(val abacus: Abacus): PluginListener {
+
+    /**
+     * The variables that are stored in the database.
+     */
+    val variables = mutableMapOf<String, NumberInterface>()
+    /**
+     * The definitions that are stored in the database.
+     */
+    val definitions = mutableMapOf<String, TreeNode>()
+
+    override fun onLoad(manager: PluginManager?) {
+
+    }
+
+    override fun onUnload(manager: PluginManager?) {
+        variables.clear()
+        definitions.clear()
+    }
+
+}

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

@@ -5,13 +5,14 @@ import org.junit.BeforeClass;
 import org.junit.Test;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
+import org.nwapw.abacus.function.DomainException;
 import org.nwapw.abacus.number.NumberInterface;
 import org.nwapw.abacus.plugin.StandardPlugin;
 import org.nwapw.abacus.tree.TreeNode;
 
 public class CalculationTests {
 
-    private static Abacus abacus = new Abacus(new Configuration(0, "precise", new String[]{}));
+    private static Abacus abacus = new Abacus(new Configuration( "precise", new String[]{}));
 
     @BeforeClass
     public static void prepareTests() {
@@ -28,11 +29,14 @@ public class CalculationTests {
         Assert.assertTrue(result.toString().startsWith(output));
     }
 
-    private void testEvalError(String input, String parseOutput) {
+    private void testDomainException(String input, String parseOutput) {
         TreeNode parsedTree = abacus.parseString(input);
         Assert.assertNotNull(parsedTree);
         Assert.assertEquals(parsedTree.toString(), parseOutput);
-        Assert.assertNull(abacus.evaluateTree(parsedTree));
+        try {
+            abacus.evaluateTree(parsedTree);
+            Assert.fail("Function did not throw DomainException.");
+        } catch (DomainException e){ }
     }
 
     @Test
@@ -73,7 +77,7 @@ public class CalculationTests {
 
     @Test
     public void testLn() {
-        testEvalError("ln(-1)", "ln((1)`)");
+        testDomainException("ln(-1)", "ln((1)`)");
         testOutput("ln2", "ln(2)", "0.6931471805599453094172321214581765680755");
     }
 
@@ -100,8 +104,8 @@ public class CalculationTests {
         testOutput("2^-1", "(2^(1)`)", "0.5");
         testOutput("2^50", "(2^50)", "112589990684262");
         testOutput("7^(-sqrt2*17)", "(7^((sqrt(2)*17))`)", "4.81354609155297814551845300063563");
-        testEvalError("0^0", "(0^0)");
-        testEvalError("(-13)^.9999", "((13)`^.9999)");
+        testDomainException("0^0", "(0^0)");
+        testDomainException("(-13)^.9999", "((13)`^.9999)");
     }
 
 }

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

@@ -17,7 +17,7 @@ import java.util.List;
 
 public class TokenizerTests {
 
-    private static Abacus abacus = new Abacus(new Configuration(0, "precise", new String[]{}));
+    private static Abacus abacus = new Abacus(new Configuration("precise", new String[]{}));
     private static LexerTokenizer lexerTokenizer = new LexerTokenizer();
     private static NumberFunction subtractFunction = new NumberFunction() {
         @Override

fx/build.gradle

@@ -1,6 +1,7 @@
 apply plugin: 'application'
 
 dependencies {
+    compile 'com.moandjiezana.toml:toml4j:0.7.1'
     compile project(':core')
 }
 

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

@@ -14,6 +14,7 @@ import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
 import org.nwapw.abacus.function.Documentation;
 import org.nwapw.abacus.function.DocumentationType;
+import org.nwapw.abacus.function.DomainException;
 import org.nwapw.abacus.number.*;
 import org.nwapw.abacus.plugin.ClassFinder;
 import org.nwapw.abacus.plugin.PluginListener;
@@ -152,6 +153,8 @@ public class AbacusController implements PluginListener {
                 return resultingString;
             } catch (ComputationInterruptedException exception) {
                 return ERR_STOP;
+            } catch (DomainException exception) {
+                return exception.getMessage();
             } catch (RuntimeException exception) {
                 exception.printStackTrace();
                 return ERR_EXCEPTION;
@@ -194,7 +197,7 @@ public class AbacusController implements PluginListener {
      */
     private final Runnable TIMER_RUNNABLE = () -> {
         try {
-            Configuration abacusConfig = abacus.getConfiguration();
+            ExtendedConfiguration abacusConfig = (ExtendedConfiguration) abacus.getConfiguration();
             if (abacusConfig.getComputationDelay() == 0) return;
             Thread.sleep((long) (abacusConfig.getComputationDelay() * 1000));
             performStop();
@@ -254,12 +257,12 @@ public class AbacusController implements PluginListener {
             if (oldValue.equals(settingsTab)) alertIfApplyNeeded(true);
         });
 
-        abacus = new Abacus(new Configuration(CONFIG_FILE));
+        abacus = new Abacus(new ExtendedConfiguration(CONFIG_FILE));
         PluginManager abacusPluginManager = abacus.getPluginManager();
         abacusPluginManager.addListener(this);
         performScan();
 
-        computationLimitField.setText(Double.toString(abacus.getConfiguration().getComputationDelay()));
+        computationLimitField.setText(Double.toString(((ExtendedConfiguration) abacus.getConfiguration()).getComputationDelay()));
         computationLimitField.textProperty().addListener((observable, oldValue, newValue) -> {
             if (!newValue.matches("(\\d+(\\.\\d*)?)?")) {
                 computationLimitField.setText(oldValue);
@@ -336,8 +339,8 @@ public class AbacusController implements PluginListener {
             if (!pluginEntry.isEnabled()) disabledPlugins.add(pluginEntry.getClassName());
         }
         if (computationLimitField.getText().matches("\\d*(\\.\\d+)?") && computationLimitField.getText().length() != 0)
-            configuration.setComputationDelay(Double.parseDouble(computationLimitField.getText()));
-        configuration.saveTo(CONFIG_FILE);
+            ((ExtendedConfiguration) configuration).setComputationDelay(Double.parseDouble(computationLimitField.getText()));
+        ((ExtendedConfiguration) configuration).saveTo(CONFIG_FILE);
         changesMade = false;
         reloadAlertShown = false;
     }

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

@@ -0,0 +1,70 @@
+package org.nwapw.abacus.fx
+
+import com.moandjiezana.toml.Toml
+import com.moandjiezana.toml.TomlWriter
+import org.nwapw.abacus.config.Configuration
+import java.io.File
+
+/**
+ * Additional settings for user interface.
+ *
+ * ExtendedConfiguration is used to add other settings
+ * that aren't built into Abacus core, but are necessary
+ * for the fx module.
+ *
+ * @property computationDelay the delay before which the computation stops.
+ * @param implementation the number implementation, same as [Configuration.numberImplementation]
+ * @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())
+    : Configuration(implementation, disabledPlugins) {
+
+    companion object {
+        /**
+         * The default TOML.
+         */
+        val DEFAULT_TOML_STRING = """
+            computationDelay=0.0
+            implementation="naive"
+            disabledPlugins=[]
+            """
+        /**
+         * A reader with the default TOML data.
+         */
+        val DEFAULT_TOML_READER = Toml().read(DEFAULT_TOML_STRING)
+        /**
+         * A writer used to writing the configuration to disk.
+         */
+        val DEFAULT_TOML_WRITER = TomlWriter()
+    }
+
+    /**
+     * Constructs a new configuration from a file on disk.
+     * @param tomlFile the file from disk to load.
+     */
+    constructor(tomlFile: File) : this() {
+        copyFrom(Toml(DEFAULT_TOML_READER).read(tomlFile).to(ExtendedConfiguration::class.java))
+    }
+
+    /**
+     * Copies data from another configuration into this one.
+     * @param config the configuration to copy from.
+     */
+    fun copyFrom(config: ExtendedConfiguration) {
+        computationDelay = config.computationDelay
+        numberImplementation = config.numberImplementation
+        disabledPlugins.clear()
+        disabledPlugins.addAll(config.disabledPlugins)
+    }
+
+    /**
+     * Saves this configuration to a file.
+     * @param file the file to save to.
+     */
+    fun saveTo(file: File) {
+        DEFAULT_TOML_WRITER.write(this, file)
+    }
+
+}