MATLAB: Does strcmp take numerical arguments

strcmp

I found an old bug in my code. I pass by mistake a numerical value to strcmp. Now, I made a little test with R2013a
    num = double('A');
    is1 = strcmp( num, {'A','B','C'} );
    is2 = strcmp( num, {'A','B','C',num} );
    is3 = strcmp( num, {'A','B','C',num2str(num)} );
    [any(is1),any(is2),any(is3)]
returns
    ans =
         0     0     0
strcmp accepts the numerical argument, but doesn't find anything. I would have appreciated an error together with a message.
On the other hand, I use a similar behavior of strfind. It takes numerical inputs.
    n1  = (65:67);
    n2  = (61:70); 
    strfind( n2, n1 ) % us' trick
returns
    ans =
         5
That is an efficient way to search for sub-sequences in row vectors of flints (whole numbers). Last millennium the difference in speed mattered.

Best Answer

I think the intent was that the semantics of strcmp be
ischar(a) && ischar(b) && strcmp(a,b)
where in that expression it obviously doesn't matter what strcmp does if either a or b is not a string. That way, when processing inputs to a function you can just write
if strcmp(opt,'high road')
and be done with it. I know that this is pretty much what I have wanted strcmp to do, and been glad that it did, on a number of occasions. Anyway, once this was the behavior, it certainly became a backward compatibility issue to change it. It is inconsistent with strfind, unfortunately, but I think strfind's behavior is also a backward compatibility thing. The help text and doc don't mention supporting non-string input.
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