undefinedp |
Discworld driver help |
undefinedp |
Name
undefinedp() - determine whether or not a given variable is undefined
Synopsis
int undefinedp( mixed arg );
Description
Return 1 if `arg' is undefined. `arg' will be undefined in the following cases:
| * | it is a variable set equal to the return value of a call_other to a non-existent method (e.g. arg = call_other(obj, "???")). | |
| * | it is a variable set equal to the return value of an access of an element in a mapping that doesn't exist (e.g. arg = map[not_there]). | |
| * | it has not yet been initialized. | |
| * | it points to a destructed object. | |
| * | it is a function (formal) parameter that corresponds to a missing actual argument. |
