Coyote Graphics Routines

Date: Fri Mar 27 12:14:20 2015

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SetDefaultValue, argument, defaultValue [, RANGE=RANGE] [, BOOLEAN=integer]

This procedure sets default values for positional and keyword arguments to IDL procedures and functions.


argument in required

The augument variable you are setting the default value of. If this variable is undefined, the defaultValue will be assigned to it. Otherwise, the argument variable will not change.

defaultValue in required

The default value that will be assigned to the argument variable ONLY if the argument variable is undefined. If this variable is undefined, the argument variable will be treated as if the BOOLEAN keyword had been set.


RANGE in optional

A two-element array that gives the accepted range of the variable. The output argument will be forced into this data range: range[0] > argument < range[1].

BOOLEAN in optional type=integer

If this keyword is set, the argument value will always be forced to return with a value of 0 or 1.


Here is how to use this program:

FUNCTION Action, arg1, arg2, MULTIPLY=multiply SetDefaultValue, arg1, 1 SetDefaultValue, arg2, 2 SetDefaultValue, multiply, 1, /BOOLEAN IF multiply THEN RETURN, arg1 * arg2 ELSE RETURN, arg1 + arg2 END

Author information



David W. Fanning 1645 Sheely Drive Fort Collins, CO 80526 USA Phone: 970-221-0438 E-mail: Coyote's Guide to IDL Programming:


Copyright (c) 2008-2014, Fanning Software Consulting, Inc.


Change History:

Written by: David W. Fanning, November 26, 2008, from suggestion by Carsten Lechte on IDL newsgroup on this date. Made a change to the way the BOOLEAN keyword works. Now argument is set to BOOLEAN before return, if required. 3 Dec 2008. DWF. Added RANGE keyword. 22 March 2014. DWF.

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