isvalidindex

int  isvalidindex(<type>&array[], int index)

int  isvalidindex(string str, int index)

Returns 1 if index is within range for the given string/array, or 0 otherwise.

This is equivalent to index < len(array) && index >= -len(array).

int  isvalidindex(dict d, string key)

Returns 1 if the key is in the dictionary, or 0 otherwise.