Add a separate class of exceptions for NumberReducer.

core/src/main/java/org/nwapw/abacus/exception/NumberReducerException.java

@@ -0,0 +1,25 @@
+package org.nwapw.abacus.exception;
+
+/**
+ * Exception thrown by the NumberReducer if something goes wrong when
+ * transforming a parse tree into a single value.
+ */
+public class NumberReducerException extends AbacusException {
+
+    /**
+     * Creates a new NumberReducerException with
+     * no additional message.
+     */
+    public NumberReducerException() {
+        this("");
+    }
+
+    /**
+     * Creates a new NumberReducerException with the given message.
+     * @param message the message.
+     */
+    public NumberReducerException(String message) {
+        super("Error evaluating expression", message);
+    }
+
+}

core/src/main/java/org/nwapw/abacus/exception/ReductionException.java

@@ -1,16 +1,14 @@
 package org.nwapw.abacus.exception;
 
 /**
- * An exception thrown primarily from Tree Value operators and functions,
- * which have to deal with the result of a Reducer as well as the results
- * of Applicable.
+ * An exception thrown from TreeReducers.
  */
-public class EvaluationException extends AbacusException {
+public class ReductionException extends AbacusException {
 
     /**
      * Creates a new EvaluationException with the default string.
      */
-    public EvaluationException() {
+    public ReductionException() {
         this("");
     }
 
@@ -18,7 +16,7 @@ public class EvaluationException extends AbacusException {
      * Creates a new EvaluationError with the given message string.
      * @param message the message string.
      */
-    public EvaluationException(String message) {
+    public ReductionException(String message) {
         super("Evaluation error", message);
     }
 

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

@@ -2,7 +2,8 @@ package org.nwapw.abacus.tree
 
 import org.nwapw.abacus.Abacus
 import org.nwapw.abacus.context.EvaluationContext
-import org.nwapw.abacus.exception.EvaluationException
+import org.nwapw.abacus.exception.NumberReducerException
+import org.nwapw.abacus.exception.ReductionException
 import org.nwapw.abacus.number.NumberInterface
 
 class NumberReducer(val abacus: Abacus, context: EvaluationContext) : Reducer<NumberInterface> {
@@ -24,7 +25,7 @@ class NumberReducer(val abacus: Abacus, context: EvaluationContext) : Reducer<Nu
                 if(variable != null) return variable
                 val definition = context.getDefinition(treeNode.variable)
                 if(definition != null) return definition.reduce(this)
-                throw EvaluationException("variable is not defined.")
+                throw NumberReducerException("variable is not defined.")
             }
             is NumberUnaryNode -> {
                 val child = children[0] as NumberInterface
@@ -57,7 +58,7 @@ class NumberReducer(val abacus: Abacus, context: EvaluationContext) : Reducer<Nu
                 abacus.pluginManager.treeValueFunctionFor(treeNode.callTo)
                         .apply(context, *treeNode.children.toTypedArray())
             }
-            else -> throw EvaluationException("unrecognized tree node.")
+            else -> throw ReductionException("unrecognized tree node.")
         }
     }
 

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

@@ -13,11 +13,8 @@ import javafx.util.StringConverter;
 import org.nwapw.abacus.Abacus;
 import org.nwapw.abacus.config.Configuration;
 import org.nwapw.abacus.exception.AbacusException;
-import org.nwapw.abacus.exception.ComputationInterruptedException;
 import org.nwapw.abacus.function.Documentation;
 import org.nwapw.abacus.function.DocumentationType;
-import org.nwapw.abacus.exception.DomainException;
-import org.nwapw.abacus.exception.EvaluationException;
 import org.nwapw.abacus.number.*;
 import org.nwapw.abacus.plugin.ClassFinder;
 import org.nwapw.abacus.plugin.PluginListener;