Difference between revisions of "Indirection (@) issues"

Latest revision as of 16:37, 18 September 2005

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Jim Self

>Kevin wrote:
>I posted about this once before, and it seems that someone had an
>answer.  But I can't find that post now.

That was me. It was in response to Nancy's question about indirection.

>I am trying to use indirection (@) to execute a callback function.
>But it looks like the indirection is limited to 8 characters.

The form of indirection you are trying is not standard nor is it supported by GT.M.

>
>e.g.
>
>GTM>w $$SIMPLE^TMGTEST("hello")
>You said:hello
>GTM>set x="SIMPLE^TMGTEST"
>
>GTM>w $$@x@("hello")
>%GTM-E-LABELMISSING, Label referenced but not defined: SIMPLE^T
>
>GTM>
>
>
>How should I do this?

Try putting the "$$" inside the quotes.

I don't think this is standard either (or documented in GT.M for that matter), but this works for me.

s test="$$ucase^%zString" 
w @test@("hello kevin")

HELLO KEVIN

Jim Self 	
Gregory wrote:
>the syntax you were trying to use is subscript indirection. It
>is used to access arrays when the array name and subscript (or
>subscripts) are stored in variables. Though there is a surface
>similarity between this syntax and that used to invoke an extrinsic
>function, function calls and array references are very different
>things in MUMPS.

Right. That is why I was suprised to find that it works at all in GT.M. Did you try it in Cache' or MUMPS_V1 or MSM?

hmmm. I just tried another test with disappointing (but not unexpected) results.

s func="$$ucase^%zString" 
s Y=@func@("hello kevin") 
w Y

That gives an error - variable expected in this context. However, the following does work.

s func="$$ucase^%zString" 
s @("Y="_func)@("hello kevin") 
w Y

The key in the examples I have tried seems to be that (in GT.M at least) if you start out with a standard form of indirection, such as argument indirection, then you can use the second @ to append subscripts or arguments to functions or subroutines.