The KEYWORD_SET function returns a byte value based on the value of the specified expression. It returns 1 (true) if its argument is defined and nonzero, and 0 (false) otherwise. The exact rules used to determine this are given in Return Value below.
Suppose that you are writing an IDL procedure that has the following procedure definition line:
PRO myproc, KEYW1 = keyw1, KEYW2 = keyw2
The following command could be used to execute a set of commands only if the keyword KEYW1 is set (i.e., it is present and nonzero):
IF KEYWORD_SET(keyw1) THEN BEGIN
The commands to be executed only if KEYW1 is set would follow.
Result = KEYWORD_SET(Expression)
This function returns 1 (true) if:
- Expression is a scalar or 1-element array with a non-zero value.
- Expression is a structure.
- Expression is an ASSOC file variable.
KEYWORD_SET returns 0 (false) if:
- Expression is undefined.
- Expression is a scalar or 1‑element array with a zero value.
The expression to be tested. Expression is usually a named variable.