IDL Problem Code 112 with alias logical-not

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Warning Problem

This is a "problem" that gets reported to let users know how that behavior might not match what they expect.

When IDL's compile options are set to idl2, idl3, or logical_predicate, it changes the way that logical operations are handled.

This warning let's you know that you should use ~ instead of not with logical comparisons in if, case, or switch statements.

compile_opt idl2

if not a then print, 'True!
 ; ^^^ warning appears here

To correct, use ~ instead

compile_opt idl2

if ~a then print, 'True!
 ; ^^ no warning!