Add a lot of comments. More to come.

src/org/nwapw/abacus/number/NaiveNumber.java

@@ -1,14 +1,30 @@
 package org.nwapw.abacus.number;
 
+/**
+ * An implementation of NumberInterface using a double.
+ */
 public class NaiveNumber implements NumberInterface {
 
+    /**
+     * The value of this number.
+     */
     private double value;
 
+    /**
+     * Creates a new NaiveNumber with the given value.
+     * @param value the value to use.
+     */
     public NaiveNumber(double value) {
         this.value = value;
     }
 
+    /**
+     * The number zero.
+     */
     public static final NaiveNumber ZERO = new NaiveNumber(0);
+    /**
+     * The number one.
+     */
     public static final NaiveNumber ONE = new NaiveNumber(1);
 
     @Override

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

@@ -1,17 +1,77 @@
 package org.nwapw.abacus.number;
 
+/**
+ * An interface used to represent a number.
+ */
 public interface NumberInterface {
 
+    /**
+     * The precision to which this number operates.
+     * @return the precision.
+     */
     int precision();
+
+    /**
+     * Multiplies this number by another, returning
+     * a new number instance.
+     * @param multiplier the multiplier
+     * @return the result of the multiplication.
+     */
     NumberInterface multiply(NumberInterface multiplier);
+    /**
+     * Divides this number by another, returning
+     * a new number instance.
+     * @param divisor the divisor
+     * @return the result of the division.
+     */
     NumberInterface divide(NumberInterface divisor);
+    /**
+     * Adds this number to another, returning
+     * a new number instance.
+     * @param summand the summand
+     * @return the result of the summation.
+     */
     NumberInterface add(NumberInterface summand);
+    /**
+     * Subtracts another number from this number,
+     * a new number instance.
+     * @param subtrahend the subtrahend.
+     * @return the result of the subtraction.
+     */
     NumberInterface subtract(NumberInterface subtrahend);
+
+    /**
+     * Returns a new instance of this number with
+     * the sign flipped.
+     * @return the new instance.
+     */
     NumberInterface negate();
+
+    /**
+     * Raises this number to an integer power.
+     * @param exponent
+     * @return
+     */
     NumberInterface intPow(int exponent);
+
+    /**
+     * Compares this number to another.
+     * @param number the number to compare to.
+     * @return same as Integer.compare();
+     */
     int compareTo(NumberInterface number);
+
+    /**
+     * Same as Math.signum().
+     * @return 1 if this number is positive, -1 if this number is negative, 0 if this number is 0.
+     */
     int signum();
 
+    /**
+     * Promotes this class to another number class.
+     * @param toClass the class to promote to.
+     * @return the resulting new instance.
+     */
     NumberInterface promoteTo(Class<? extends NumberInterface> toClass);
 
 }