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Re: CONTINUE from function within loop [message #86479 is a reply to message #86478]

Tue, 12 November 2013 21:40

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

On Wednesday, November 13, 2013 12:19:43 AM UTC-5, Sebastian Luque wrote:
> Hi,
>
>
>
> I read the CATCH and ON_ERROR help pages, but I can't see how to handle the following situation. Say we have a FOR loop where a function is called for each iteration:
>
>
>
> FOR i=0, 10 DO BEGIN
>
> print, myfun(i)
>
> ENDFOR
>
>
>
> I would like MYFUN to continue with the next iteration if it runs into an error. Naively, this should show what I'm looking for:
>
>
>
> FUNCTION MYFUN, X
> [BODY]
> IF [condition] THEN BEGIN
> message, 'A problem with X', /informational
> CONTINUE
> ENDIF
> [REST IF OK]
> RETURN, [something]
> END
>
> But, of course, CONTINUE only works within an FOR/ENDFOR block, not this way. How does one accomplish this?

You're right, because CONTINUE only works within the same lexical scope.

You could do this by putting a CATCH within your main loop, which will catch your MESSAGE within MYFUN. That's a little dangerous because it will catch *every* error though.

A better practice is to return a separate status variable MYFUN indicating success or failure, and have the main loop check the variable and decide what to do.

Something like this...
function myfun, x, status=status
status = -1
;; Failure case
if [condition] then return, !values,d_nan
[ rest of MYFUN ]
;; Success case
status = 1
return, [something]
end

for i = 0, 10 do begin
y = myfun(x, status=status)
if status LT 0 then continue
print, y
endfor

Craig

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[Message index]

		CONTINUE from function within loop By: spluque on Tue, 12 November 2013 21:19
		Re: CONTINUE from function within loop By: Craig Markwardt on Tue, 12 November 2013 21:40
		Re: CONTINUE from function within loop By: spluque on Wed, 13 November 2013 07:21
		Re: CONTINUE from function within loop By: Moritz Fischer on Tue, 12 November 2013 22:32

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