$function vs $$function

Question

Question

Ponnumani Gurusamy · Aug 17, 2016

#ObjectScript #Caché

What are the difference between $ and $$ symbols using macro.

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Dmitry Maslennikov · Aug 17, 2016

Macro is $$$. Anyway, a little excerpt from documentation

$

Dollar sign (36): Intrinsic (system) function prefix: $name(parameters).

Special variable prefix: $name.

$Znnn (a name beginning with $Z) can be a user-defined function or special variable defined using %ZLANG language extension library. It can also be an intrinsic (InterSystems supplied) function or special variable.

Regular expression end of string anchor; for example, (USA)$.

In ZBREAK debugging, a single-step breakpoint.

As first character at terminal prompt, load interactive subshell.

$$

Double dollar sign: Extrinsic (user-written) function prefix: $$name(parameters). $$ is returned by $STACK when context was established by an extrinsic function reference.

Prefix to a routine name to directly invoke that routine.

$$$

Triple dollar sign: Macro invocation prefix.

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score 3 · Answer 1 · 2016-09-09T14:56:34-04:00

On a related note, here is a useful appendix that you can use to figure out things like this:

http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...

"As you read existing Caché ObjectScript code, you may encounter unfamiliar syntax forms. This appendix shows syntax forms in different groups, and it explains what they are and where to find more information."