NAME
IsValidListIndex — Check whether the given value works as an index.
SYNOPSIS
IsValidListIndex ListValue Index
DESCRIPTION
Return Value
1 Value can be used to index list.
0 Value cannot be used to index list.
Arguments
ListValueList to check whether value can be an index of.
IndexValue to check whether it can be an index into the list.

For information regarding exceptions / errors, see here.
EXAMPLES 
% IsValidListIndex [list 1 2 3] 2
1
% IsValidListIndex [list 4 5 6] 3
0
SEE ALSO
llength
KEYWORDS
check, list, validation, verification