| passing multiple keywords to subroutines [message #14109] |
Thu, 21 January 1999 00:00 |
David Ritscher
Messages: 30
Registered: August 1995
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Member |
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It's often desirable to redefine a function, and then have this new
function behave almost like the original function. To cook up an
example, let's say I need a new plot function, that plots the x-axis
as .001 units:
pro myplot, x
plot, findgen(n_elements(x) * 0.001), x
return
end
It would now be great to be able to pass any and all possible keywords
into this new plotting function, so I might call it as:
myplot, x, title='test', linestyle=3
In IDL, this can be done by including all possible keywords (rather
tedious!) In PV-Wave, it's almost impossible, since it is not
possible to pass in an undefined keyword:
(I have not defined the variable 'color' here:)
WAVE> plot, [1,5], color=color
% PLOT: Variable is undefined: COLOR.
% Execution halted at $MAIN$ (PLOT).
This same command works fine in IDL, and has the appropriate behavior
(Here, with 'color' undefined, it behaves exactly the same as if the
keyword was not specified).
Thus in IDL it is possible to define my new function along these lines:
pro myplot, x, color=color, linestyle=linestyle, ynozero=ynozero, $
noclip=noclip, yrange=yrange,
...
As I say, this becomes rather tedious.
Does anyone see a simpler way to handle this sort of thing? It seems
to me that that two things are needed:
1. both companies need to add a mechanism to handle keywords that will
be passed on to subroutines, which might take on a form like the
following:
pro pass_keywords=pass_keywords myplot, x
plot, x, pass_keywords=pass_keywords
where I can now call 'myplot' with extra keywords:
myplot, x, linestyle=3
2. The bugs in PV-Wave have to be fixed, such that undefined keywords
can be handled by every function.
Am I missing a better way to handle these issues?
David Ritscher
--
Cardiac Rhythm Management Laboratory
Department of Medicine
University of Alabama at Birmingham
B168 Volker Hall - 1670 University Boulevard
Birmingham AL 35294-0019
Tel: (205) 975-2122 Fax: (205) 975-4720
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