MATLAB Central Newsreader - Compare strings of different lengths without using strcmp?

Compare strings of different lengths without using strcmp?

NouveauIX — Thu, 24 Sep 2009 20:09:00 -0400

I'm trying to compare two strings with if statements without using strcmp.

function log=myStrCmpI(char1,char2)
c1=lower(char1);
c2=lower(char2);
if ?
log=true;
else log=false;
end

I tried taking the sum of c1-c2 but that doesn't work for all cases, such as if the strings are the same but have a couple letters switched around.

Re: Compare strings of different lengths without using strcmp?

dpb — Thu, 24 Sep 2009 20:10:15 -0400

NouveauIX wrote:
> I'm trying to compare two strings with if statements without using strcmp.
>
> function log=myStrCmpI(char1,char2)
> c1=lower(char1);
> c2=lower(char2);
> if ?
> log=true;
...
Well, one has to start w/ a clear definition of what the criterion for
equality would be. If the two aren't the same length, then they
obviously can't be identical so what would "true" be indicating, anyway?

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Re: Compare strings of different lengths without using strcmp?

dpb — Thu, 24 Sep 2009 20:16:19 -0400

dpb wrote:
...
> Well, one has to start w/ a clear definition of what the criterion for
> equality would be. If the two aren't the same length, then they
> obviously can't be identical so what would "true" be indicating, anyway?

OBTW, if they are the same length,

flg = all(s2==s1);

If they're not, again, "Houston, we have a dimensions problem"...

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Re: Compare strings of different lengths without using strcmp?

NouveauIX — Fri, 25 Sep 2009 05:28:52 -0400

Oh I'm sorry. They need to be equal disregarding case. So 'banana' and 'BaNana' would be equal, as would 'purple' and 'purple'. Result is true if the strings are equal, false if not. I need to be able to enter strings of lengths that aren't equal, though, even if the result will be false.

Re: Compare strings of different lengths without using strcmp?

Jan Simon — Fri, 25 Sep 2009 07:32:04 -0400

Dear NouveauIX!

> I'm trying to compare two strings with if statements without using strcmp.
>
> function log=myStrCmpI(char1,char2)
> c1=lower(char1);
> c2=lower(char2);
> if ?
> log=true;
> else log=false;
> end

  function Log = myStrCmpI(char1,char2)
  Log = (numel(char1) == numel(char2)) && ...
           all(lower(char1) == lower(char2));
  return;

1. The && operator performs short-circuiting: the 2nd part of the comparison is not evaluated, if the 1st is FALSE already. This is important.
2. I've renamed "log" to "Log" to reduce conflicts with Matlab's logarithm function. Although this is not an error, it is worth to avoid as many confusions as possible...

Finally: STRCMPI is really fast and does check the types of the inputs. This can be a tremendous help for debugging! In addition STRCMPI works for cell strings also and cares about CHAR arrays with more than 1 row.

Good luck, Jan

Re: Compare strings of different lengths without using strcmp?

Loren Shure — Fri, 25 Sep 2009 17:41:06 -0400

In article
<1257816834.5891.1253856562126.JavaMail.root@gallium.mathforum.org>,
visualxd@gmail.com says...
> Oh I'm sorry. They need to be equal disregarding case. So 'banana' and 'BaNana' would be equal, as would 'purple' and 'purple'. Result is true if the strings are equal, false if not. I need to be able to enter strings of lengths that aren't equal, though, even if the result will be false.
>

Have you looked at strcmpi - which allows you to compare strings in a
case-insensitive manner.

--
Loren
http://blogs.mathworks.com/loren