uncertain number of loop structures
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Here is my problem:
the function has uncertain number of inputs, while the number of loop structures depends on the number of inputs. For example, if there is only one input, then only one loop structure is needed, two inputs, two loop structures, ...
I know how to deal with uncertain inputs, but need help to code uncertain number of loop structures.
Leon
2 commentaires
Sean de Wolski
le 5 Mai 2011
What are the loops doing? It's quite possible to avoid the loops altogether which makes the whole problem irrelevant. Paste a snippet of code and the problem for us to see!
Walter Roberson
le 24 Août 2012
(Re-opened as the question is of sufficient general interest and the answers give enough information to be useful.)
Réponses (4)
the cyclist
le 5 Mai 2011
I agree with Sean de, that you may be able to avoid the loops with some more clever programming, so you might want to post some code.
However, once upon a time, I had to do exactly what you are asking. It can be done with the eval() function. Here is a trivial example that will give you the idea:
NDIM = 4;
forString = [];
doString = [];
endString = [];
for nd = 1:NDIM
forString = ['for i',num2str(nd),'=1:10,',forString];
doString = ['disp(i',num2str(nd),');',doString];
endString = [endString,'end;']; %#ok<AGROW>
end
loopString = [forString,doString,endString];
eval(loopString);
1 commentaire
Sean de Wolski
le 5 Mai 2011
Of course to avoid using evil eval, if you know what the maximum number of loops possibly necessary is, you could just have that many written out and skip all of the interior ones you don't need.
Sean de Wolski
le 5 Mai 2011
Or one could use fprintf along the same lines as The Cyclist's suggestion to generate a custom m-file for each number of dimensions applicable. Then when the user enters the number of dimensions that m-file is called.
0 commentaires
Liang
le 5 Mai 2011
2 commentaires
Daniel Shub
le 5 Mai 2011
Are you just trying to get to the final "i"? It doesn't even look like you need while loops. You should be able to loop over (or probably even nest) a bunch of "find" commands.
Daniel Shub
le 5 Mai 2011
function looper(FcnHandle, NDIM, LoopIndices, Array)
LoopNo = length(Array)+1;
if LoopNo == NDIM
for ii = LoopIndices{LoopNo}
Array{LoopNo} = ii;
FcnHandle(Array)
end
else
for ii = LoopIndices{LoopNo}
Array{LoopNo} = ii;
looper(FcnHandle, NDIM, LoopIndices, Array)
end
end
end
looper(@(x)(disp(num2str([x{:}]))), 3, {1:3, 1:3, 1:3}, {})
1 commentaire
Daniel Shub
le 5 Mai 2011
Opps, this doesn't answer the revised question. I think it does what Cyclist did without eval or knowing the maximum number of loops.
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