math.functions: adding docs and tests for ^mod.

basis/math/functions/functions-docs.factor

@@ -292,6 +292,10 @@ HELP: mod-inv
     { $example "USING: math prettyprint ;" "173 815 * 1119 mod ." "1" }
 } ;
 
+HELP: ^mod
+{ $values { "x" real } { "y" real } { "n" real } { "z" real } }
+{ $description "Outputs the result of computing " { $snippet "x^y mod n" } "." } ;
+
 HELP: ~
 { $values { "x" real } { "y" real } { "epsilon" real } { "?" "a boolean" } }
 { $description "Tests if " { $snippet "x" } " and " { $snippet "y" } " are approximately equal to each other. There are three possible comparison tests, chosen based on the sign of " { $snippet "epsilon" } ":"

basis/math/functions/functions-tests.factor

@@ -178,6 +178,8 @@ CONSTANT: log10-factorial-1000 0x1.40f3593ed6f8ep11
 
 [ 2 10 mod-inv ] must-fail
 
+[ t ] [ 15 37 137 ^mod 15 37 ^ 137 mod = ] unit-test
+
 [ t ] [ 0 0 ^ fp-nan? ] unit-test
 [ 1 ] [ 10 0 ^ ] unit-test
 [ 1/8 ] [ 1/2 3 ^ ] unit-test