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Re: [PATCH] Add min/max tests. (4/4)
From: |
John W. Eaton |
Subject: |
Re: [PATCH] Add min/max tests. (4/4) |
Date: |
Tue, 5 Sep 2000 22:54:43 -0500 (CDT) |
On 4-Sep-2000, Edward Jason Riedy <address@hidden> wrote:
| And "John W. Eaton" writes:
| - I think that
| [...]
| - is much less surprising than
| [...]
| - since -2 is smaller than 1 [...]
|
| Not in magnitude. I suppose that's the key.
|
| I just realized the behavior I want to avoid still occurs. Imagine
| a nice long calculation intended for complex matrices and magnitude
| comparisons written with min / max. Now imagine that a column just
| happens to become all real... I wouldn't want to try to debug that
| problem.
|
| Unfortunately, it still happens when a matrix becomes all real ``by
| accident,'' so there does need to be a way to specify magnitude
| comparisons to min / max.
How about
min (abs (x), abs (y))
?
If I recall correctly, it doesn't really make sense to ask whether one
complex number is `less than' another. That Matlab overloads the
relational operators to mean X op Y == abs(X) op abs(Y) is, I believe,
just a convention. Someone (presumably Cleve Moler) thought it would
be a convenient shorthand. I suppose it is in some cases, but it also
introduces some ambiguity and surprising results (something of a
running theme in the design of Matlab, if you ask me).
If it were up to me (or if I could do it over again) I'd say that min,
max, <, <=, >, >= have no meaning for complex numbers in Octave, and
that if you want to compare magnitudes, you have to state that
explicitly.
jwe
- [PATCH] Add min/max tests. (4/4), Edward Jason Riedy, 2000/09/04
- [PATCH] Add min/max tests. (4/4), John W. Eaton, 2000/09/04
- Re: [PATCH] Add min/max tests. (4/4), Edward Jason Riedy, 2000/09/04
- Re: [PATCH] Add min/max tests. (4/4),
John W. Eaton <=
- Re: [PATCH] Add min/max tests. (4/4), John W. Eaton, 2000/09/06
- Re: [PATCH] Add min/max tests. (4/4), Edward Jason Riedy, 2000/09/13
- Re: [PATCH] Add min/max tests. (4/4), John W. Eaton, 2000/09/13
- Re: [PATCH] Add min/max tests. (4/4), Edward Jason Riedy, 2000/09/13
- Python (was: Re: [PATCH] Add min/max tests. (4/4)), John W. Eaton, 2000/09/13
- Re: Python (was: Re: [PATCH] Add min/max tests. (4/4)), Edward Jason Riedy, 2000/09/14