Le 23/11/2019 à 15:35, Samuel Gougeon a écrit :
HelloPhilipp, and to all (former ;-) matlabers,
Le 16/10/2019 à 11:46, P M a écrit :
Dear experts,
trying to convert a matlab code to scilab I come across following line:
[~,~,Minstances_hat] = unique(B(:));
How to replace the "~" symbol?
B is the blue channel of a RGB image...hence a m x n matrix of
integers (type(B) = 8 )
This issue is now reported as bug 16250
<http://bugzilla.scilab.org/show_bug.cgi?id=16254>.
Solving this issue would improve the converter.
I may contribute to solve it. However, I do not use to use Matlab or
Octave. So i don't know how the ~ placeholder set in the list of
/inputs/ is processed inside the called function. This message is a
call for information about this topic.
Ignoring an output is trivial. As suggested by Stéphane, the ans
variable is a good candidate as replacement for ~,
just as a fake recipient, as in "[~, ia] = unique(A)" => "[ans, ia]
= unique(A)"
The meaning of ignoring an input is a priori completely different, at
least from a Scilab point of view.
This leads to the fact that, on the "function ..." line, the converter
will have to distinguish the list of inputs from the list of outputs,
and then process the same ~ character in 2 different ways.
This processing would have to run also when the "function ..." line is
split on several rows with the "..." continuation marks.
First, i will need an actual example of function call with ~ in the
input list, runnable in Octave.
Any compact suggestion is welcome.
At least 2 use cases are expected: one calling a function written in
Octave/Matlab language (improperly called "macros" in Scilab), the
other one calling a hard-coded function.
Let's consider the first case, with a "macro":
* What does the ~ sent placeholder pass to the function? How is it
detected/detectable inside the macro ?
* How is it processed by the function? Is there a generic default
processing, as replacing it with the empty matrix [], or whatever
else?
Where is the crowd of matlabers?
The page describing this feature:
https://fr.mathworks.com/help/matlab/matlab_prog/ignore-function-inputs.html
But i do not clearly understand it.
Apparently, "canceling" an input is done (only?) at the function
definition, not when calling it, unlike for the outputs.
If so, then /ans/ could also be used as a replacement, meaning that
anyway this input won't be used inside the function.
A test of call with Octave yields an error:
>> function [r, s] = funtest(a,b,c)
end
>> funtest(1,~,3)
parse error:
invalid use of empty argument (~) in index expression
>>> funtest(1,~,3)
^
>>
Any further insight is welcome.
Samuel
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