remove limits from fact in favour of estimation. Fixes #1065

docs/scarpet/language/Math.md

@@ -6,11 +6,12 @@ There is bunch of them - they require a number and spit out a number, doing what
 
 ### `fact(n)`
 
-Factorial of a number, a.k.a `n!`, just not in `scarpet`. Gets big... quick...
+Factorial of a number, a.k.a `n!`, just not in `scarpet`. Gets big... quick... Therefore, values larger 
+than `fact(20)` will not return the exact value, but a value with 'double-float' precision.
 
 ### `sqrt(n)`
 
-Square root. For other fancy roots, use `^`, math and yo noggin. Imagine square roots on a tree...
+Square root (not 'a squirt') of a number. For other fancy roots, use `^`, math and yo noggin. Imagine square roots on a tree...
 
 ### `abs(n)`
 

src/main/java/carpet/script/language/Arithmetic.java

@@ -20,12 +20,23 @@ public class Arithmetic {
         expression.addUnaryFunction("fact", (v) ->
         {
             long number = NumericValue.asNumber(v).getLong();
-            long factorial = 1;
+            if (number < 21)
+            {
+                long factorial = 1;
+                for (int i = 1; i <= number; i++)
+                {
+                    factorial = factorial * i;
+                }
+                return new NumericValue(factorial);
+            }
+            // values over 21 will exceed long limits
+            double factorial = 1.0;
             for (int i = 1; i <= number; i++)
             {
                 factorial = factorial * i;
             }
             return new NumericValue(factorial);
+
         });
         expression.addMathematicalUnaryFunction("sin",    (d) -> Math.sin(Math.toRadians(d)));
         expression.addMathematicalUnaryFunction("cos",    (d) -> Math.cos(Math.toRadians(d)));