Factorial Function

::---------------------------------------------------------------------------------------
::  Get the factorial of a number
::
:: call :factorial 7 RETURNVAR
:: echo %RETURNVAR%
::---------------------------------------------------------------------------------------
:factorial
    setlocal
        set "out=1"

        for /l %%a in (%~1,-1,1) do set /a "out*=%%a"
        if %~1 equ 0 set "out=1"

        (endlocal
            if "%~2" neq "" ( set "%~2=%out%" ) else echo %out%
        )
goto :eof
::---------------------------------------------------------------------------------------