Rescan the plugins folder.

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

@@ -255,13 +255,7 @@ public class AbacusController implements PluginListener {
         abacus = new Abacus(new Configuration(CONFIG_FILE));
         PluginManager abacusPluginManager = abacus.getPluginManager();
         abacusPluginManager.addListener(this);
-        abacusPluginManager.addInstantiated(new StandardPlugin(abacus.getPluginManager()));
+        performScan();
-        try {
-            ClassFinder.loadJars("plugins").forEach(abacusPluginManager::addClass);
-        } catch (IOException | ClassNotFoundException e) {
-            e.printStackTrace();
-        }
-        abacusPluginManager.reload();
 
         computationLimitField.setText(Double.toString(abacus.getConfiguration().getComputationDelay()));
         computationLimitField.textProperty().addListener((observable, oldValue, newValue) -> {
@@ -311,6 +305,19 @@ public class AbacusController implements PluginListener {
         reloadAlertShown = false;
     }
 
+    @FXML
+    public void performScan(){
+        PluginManager abacusPluginManager = abacus.getPluginManager();
+        abacusPluginManager.removeAll();
+        abacusPluginManager.addInstantiated(new StandardPlugin(abacus.getPluginManager()));
+        try {
+            ClassFinder.loadJars("plugins").forEach(abacusPluginManager::addClass);
+        } catch (IOException | ClassNotFoundException e) {
+            e.printStackTrace();
+        }
+        abacusPluginManager.reload();
+    }
+
     @FXML
     public void performReload() {
         alertIfApplyNeeded(true);

src/main/java/org/nwapw/abacus/number/NumberInterface.java

@@ -240,6 +240,7 @@ public abstract class NumberInterface {
      * @param toClass the class to promote to.
      * @return the resulting new instance.
      */
+    @Deprecated
     protected abstract NumberInterface promoteToInternal(Class<? extends NumberInterface> toClass);
 
     /**
@@ -250,6 +251,7 @@ public abstract class NumberInterface {
      * @param toClass the class to promote to.
      * @return the resulting new instance.
      */
+    @Deprecated
     public final NumberInterface promoteTo(Class<? extends NumberInterface> toClass) {
         checkInterrupted();
         return promoteToInternal(toClass);

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

@@ -14,7 +14,7 @@ public abstract class NumberImplementation {
     /**
      * The list of paths through which this implementation can be promoted.
      */
-    protected Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> promotionPaths;
+    private Map<Class<? extends NumberInterface>, Function<NumberInterface, NumberInterface>> promotionPaths;
     /**
      * The implementation class for this implementation.
      */

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

@@ -187,6 +187,24 @@ public class PluginManager {
         }
     }
 
+    /**
+     * Removes the plugin with the given class from the manager.
+     * @param toRemove the plugin to remove.
+     */
+    public void removeClass(Class<? extends Plugin> toRemove){
+        if(!loadedPluginClasses.contains(toRemove)) return;
+        plugins.removeIf(plugin -> plugin.getClass() == toRemove);
+        loadedPluginClasses.remove(toRemove);
+    }
+
+    /**
+     * Removes all plugins from this plugin manager.
+     */
+    public void removeAll(){
+        loadedPluginClasses.clear();
+        plugins.clear();
+    }
+
     /**
      * Loads all the plugins in the PluginManager.
      */

src/main/java/org/nwapw/abacus/tree/Reducer.java

@@ -1,19 +0,0 @@
-package org.nwapw.abacus.tree;
-
-/**
- * Interface used to reduce a tree into a single value.
- *
- * @param <T> the value to reduce into.
- */
-public interface Reducer<T> {
-
-    /**
-     * Reduces the given tree into a single value of type T.
-     *
-     * @param node     the node being passed in to be reduced.
-     * @param children the already-reduced children of this node.
-     * @return the resulting value from the reduce.
-     */
-    public T reduceNode(TreeNode node, Object... children);
-
-}

src/main/kotlin/org/nwapw/abacus/tree/FunctionNode.kt

@@ -16,7 +16,7 @@ data class FunctionNode(val function: String) : TreeNode() {
     val children: MutableList<TreeNode> = mutableListOf()
 
     override fun <T : Any> reduce(reducer: Reducer<T>): T? {
-        val children = Array<Any?>(children.size, { children[it].reduce(reducer) ?: return null; })
+        val children = Array<Any>(children.size, { children[it].reduce(reducer) ?: return null; })
         return reducer.reduceNode(this, *children)
     }
 

src/main/kotlin/org/nwapw/abacus/tree/Reducer.kt

@@ -0,0 +1,19 @@
+package org.nwapw.abacus.tree
+
+/**
+ * Reducer interface that takes a tree and returns a single value.
+ *
+ * The reducer walks the tree, visiting the children first, converting them into
+ * a value, and then attempts to reduce the parent. Eventually, the single final value is returned.
+ */
+interface Reducer <out T> {
+
+    /**
+     * Reduces the given tree node, given its already reduced children.
+     *
+     * @param treeNode the tree node to reduce.
+     * @param children the list of children, of type T.
+     */
+    fun reduceNode(treeNode: TreeNode, vararg children: Any) : T?
+
+}

src/main/resources/abacus.fxml

@@ -57,6 +57,7 @@
                         <Button text="Apply" onAction="#performSave"/>
                         <Button text="Reload Plugins" onAction="#performReload"/>
                         <Button text="Apply and Reload" onAction="#performSaveAndReload"/>
+                        <Button text="Scan Plugins" onAction="#performScan"/>
                     </FlowPane>
                 </GridPane>
             </Tab>