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RE: Small problem in a if condition
From: |
THOMAS Paul Richard |
Subject: |
RE: Small problem in a if condition |
Date: |
Mon, 2 Feb 2004 17:35:07 +0100 |
John,
For what it is worth, I just checked that Matlab 5 and Matlab 6 do an
implicit double() on the the character in the condition (both rhs and lhs).
That is to say, setting x=63 gives a true.
Regards
Paul
-----Message d'origine-----
De : John W. Eaton [mailto:address@hidden
Envoyé : lundi 2 février 2004 16:49
À : Pol
Cc : address@hidden
Objet : Re: Small problem in a if condition
On 2-Feb-2004, Pol <address@hidden> wrote:
| On Sun, 1 Feb 2004 11:12:27 -0600
|
| "John W. Eaton" <address@hidden> wrote:
|
| > What version of Octave are you using? I think the == operator should
| > work for character strings with either 2.0.17 or 2.1.50.
|
| [~]$ octave --version
| GNU Octave, version 2.1.50 (i686-pc-linux-gnu).
OK, I see now that the problem in your function was that you were
doing something like this:
x = 1;
if (x == "?")
...
endif
This doesn't work in 2.1.50, but does in the current sources (and
probably 2.1.53, though I haven't checked).
So the current behavior is that for a mixed-type comparison like
this, the test will return true if the ASCII value of the character is
equal to the integer. So in the above, if X is 63, then the body of
the IF block will be executed. I guess we are getting closer to
bug-for-bug compatibility. Is this really what people want?
I suspect that this behavior leads to subtle bugs as many people
will think that what the == operator is doing is the equivalent of
isstr (x) && x == "?" ## this is what strcmp does
instead of
x == toascii ("?")
Just out of curiosity, how did you expect the == tests in your code to
behave?
jwe
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