Merge branch 'master' of https://github.com/DanilaFe/abacus

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

@@ -7,7 +7,6 @@ public class FunctionDatabase {
     private HashMap<String, Function> functions;
 
     private void registerDefault(){
-
         functions.put("+", new Function() {
             @Override
             protected boolean matchesParams(Number[] params) {
@@ -63,6 +62,25 @@ public class FunctionDatabase {
                 return params[0].divide(params[1]);
             }
         });
+
+        functions.put("!", new Function() {
+            @Override
+            protected boolean matchesParams(Number[] params) {
+                return params.length == 1;
+            }
+
+            @Override
+            protected Number applyInternal(Number[] params) {
+                Number factorial = params[0];
+                Number multiplier = params[0];
+                //It is necessary to later prevent calls of factorial on anything but non-negative integers.
+                while(multiplier.signum() == 1){
+                    multiplier = multiplier.subtract(NaiveNumber.ONE.promoteTo(multiplier.getClass()));
+                    factorial = factorial.multiply(multiplier);
+                }
+                return factorial;
+            }
+        });
     }
 
     public FunctionDatabase(){

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

@@ -8,6 +8,9 @@ public class NaiveNumber implements Number {
         this.value = value;
     }
 
+    static final NaiveNumber ZERO = new NaiveNumber(0);
+    static final NaiveNumber ONE = new NaiveNumber(1);
+
     @Override
     public int precision() {
         return 4;
@@ -39,13 +42,14 @@ public class NaiveNumber implements Number {
     }
 
     @Override
-    public Number zero() {
-        return new NaiveNumber(0);
+    public int compareTo(Number number) {
+        NaiveNumber num = (NaiveNumber) number;
+        return Double.compare(value, num.value);
     }
 
     @Override
-    public Number one() {
-        return new NaiveNumber(1);
+    public int signum() {
+        return this.compareTo(ZERO);
     }
 
     @Override
@@ -53,5 +57,6 @@ public class NaiveNumber implements Number {
         if(toClass == this.getClass()) return this;
         return null;
     }
+
 }
 

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

@@ -8,9 +8,8 @@ public interface Number {
     Number add(Number summand);
     Number subtract(Number subtrahend);
     Number negate();
-
-    Number zero();
-    Number one();
+    int compareTo(Number number);
+    int signum();
 
     Number promoteTo(Class<? extends Number> toClass);