Add a lot of comments. More to come.

src/org/nwapw/abacus/function/Function.java

@@ -5,16 +5,40 @@ import org.nwapw.abacus.number.NumberInterface;
 
 import java.util.HashMap;
 
+/**
+ * A function that operates on one or more
+ * inputs and returns a single number.
+ */
 public abstract class Function {
 
+    /**
+     * A map to correctly promote different number implementations to each other.
+     */
     private static final HashMap<Class<? extends NumberInterface>, Integer> priorityMap =
             new HashMap<Class<? extends NumberInterface>, Integer>() {{
                 put(NaiveNumber.class, 0);
             }};
 
+    /**
+     * Checks whether the given params will work for the given function.
+     * @param params the given params
+     * @return true if the params can be used with this function.
+     */
     protected abstract boolean matchesParams(NumberInterface[] params);
+
+    /**
+     * Internal apply implementation, which already receives appropriately promoted
+     * parameters that have bee run through matchesParams
+     * @param params the promoted parameters.
+     * @return the return value of the function.
+     */
     protected abstract NumberInterface applyInternal(NumberInterface[] params);
 
+    /**
+     * Function to check, promote arguments and run the function.
+     * @param params the raw input parameters.
+     * @return the return value of the function, or null if an error occurred.
+     */
     public NumberInterface apply(NumberInterface...params) {
         if(!matchesParams(params)) return null;
         return applyInternal(params);