| Re: HELP: Multiple-file Applications [message #3204] |
Tue, 06 December 1994 08:05  |
djackson
Messages: 31
Registered: June 1993
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Member |
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James Tappin writes:
> However if your code is a routine rather than a main program then you
> can use CALL_PROCEDURE or CALL_FUNCTION to compile (if not already
> compiled) and execute it (these are more efficient than EXECUTE).
Norbert Hahn writes:
> I played a little with CALL_PROCEDURE and it seems to do what you like.
> I wrote
> sub = 'fader'
> and typed
> call_procedure, sub, out=0.25
[note: I'm not actually worried about variable procedure compilation,
I know what I want to be compiled, but _when/if_ it's compiled
is to be left to run-time. No harm done, it's the same
otherwise.]
> and noticed that fader.pro was found in the search path, compiled and
> executed.
>
> Note that IDL only compiles those procedure that haven't been compiled
> before in this session
>
> and
>
> that IDL only compiles the file including all procedure contained there
> *until* it has reached the END statement of the procedure requested.
>
> Thus, if you have nested procedures, it is best to put the outermost
> procedure (that's the one you call explicitly) at the end of the file.
This sounds good, and I didn't come to the same conclusion, since I
confused myself (and found another 'gotcha' here) by writing these test
routines, caller.pro and helper.pro: (bear with me!)
::::::::::::::
caller.pro
::::::::::::::
pro caller
a = randomu(seed) + 1.0
help, a, helper(a)
pre_pre_helper, a
help, pre_helper(a)
end
::::::::::::::
helper.pro
::::::::::::::
pro pre_pre_helper, x
print, "In pre_pre_helper, X =", x
end
function pre_helper, x
return, x+42.4242
end
function helper, x
return, pre_helper(x)/2.02
end
function post_helper, x
return, -x
end
Then, to test them in a fresh IDL session:
IDL> caller
% Compiled module: CALLER.
% Compiled module: HELPER.
A FLOAT = 1.23121
<Expression> FLOAT = 21.6116
In pre_pre_helper, X = 1.23121
---***--- OK, in CALLER, that one was compiled as a procedure call,
then the procedure was compiled.
% Variable is undefined: PRE_HELPER.
---***--- This is the 'gotcha': when CALLER was compiled, PRE_HELPER
looked
like an array variable, since no function yet existed, I
suppose.
% Execution halted at CALLER <caller.pro( 7)> .
% Called from $MAIN$ .
IDL> help,pre_helper(3)
<Expression> FLOAT = 45.4242
IDL> help,post_helper(3)
% Variable is undefined: POST_HELPER.
% Execution halted at CALLER <caller.pro( 7)> .
% Called from $MAIN$ .
IDL>
So, having multiple routines in a 'subordinate' file, and calling the
last one found in there first, will cause all the others to work
thereafter, unless there are functions, in which case they'll look like
array variables. It's a bit constraining, but if I keep it strictly
modular, so only the last pro/function in the 'subordinate' file is
called from outside, then I'll be OK.
Thanks so far, any other tips? There must be lots of big widget-app
builders out there.
Cheers,
-Dick
Dick Jackson djackson@ibd.nrc.ca Institute for Biodiagnostics
Opinions are mine alone. National Research Council Canada, Winnipeg
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