< Making an IDL Variable Undefined
Coyote's Guide to IDL Programming

Making an IDL Variable Undefined

QUESTION: How do I make an IDL variable have a type "undefined"?

ANSWER: At the main IDL level you can use the IDL procedure DELVAR to delete an IDL variable and make it undefined. Inside of procedures and functions, I use this little program named UNDEFINE that I got from Andrew Cool at the DSTO High Frequency Radar Division in Adelaide, Australia.

   PRO UNDEFINE, varname  
   tempvar = SIZE(TEMPORARY(varname))
   END

You use it like this:

   IDL> a = BYTARR(200,200)
   IDL> HELP, a

   A    BYTE = Array(200, 200)

   IDL> UNDEFINE, a
   IDL> HELP, a

   A   UNDEFINED = *Undefined*

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