coyote: SETDEFAULTVALUE

Description
This procedure sets default values for positional and keyword arguments to
IDL procedures and functions.
Categories
Utilities
Params
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.
Keywords
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.
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].
Examples
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
FANNING SOFTWARE CONSULTING::
   David W. Fanning
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com
History
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.
Copyright
Copyright (c) 2008-2014, Fanning Software Consulting, Inc.