Returns a non-zero number if the specified function exists in the script.
MinParamsPlus1 := IsFunc(FunctionName)
The name of the function whose minimum number of parameters is retrieved. FunctionName must exist explicitly in the script. FunctionName can be a function reference instead of a name.
This function returns one plus the minimum number of parameters (e.g. 1 for a function that requires zero parameters, 2 for a function that requires 1 parameter, etc.). If FunctionName does not exist explicitly in the script (by means such as #Include or a non-dynamic call to a library function), it returns 0.
Dynamically Calling a Function, Function References, Func Object, Func, A_ThisFunc
count := IsFunc("RegExReplace") ; Any function name can used here.
if count
MsgBox "This function exists and has " count-1 " mandatory parameters."
else
MsgBox "This function does not exist."