[MATRIX-SIG] umath.logical_blah vs normal python functions.

[David J. C. Beach]

Anthony Baxter wrote:

> is there any reason for this difference in behaviour? It's unexpected (well, it
> was unexpected by me :)
>
> >>> umath.logical_and(4,5)
> 1
> >>> 4 and 5
> 5

>>> 4 and 5
5

4 is true, so return the value of the second operand, which is 5.  But that's okay
because 5 is a true value.  Since and here is a language construct, you can say
nifty things like

>>> go_to_your_room() and clean_up_the_mess()

and still get the return value from the second (assuming go_to_your_room() was
true)

>>> umath.logical_and(4, 5)
1

4 and 5 are both true, so logical_and returns a 1, which is true.

and, if you want a bitwise and,

>>> umath.boolean_and(4, 5)
4

the bitwise and of the binary representations for 4 and 5.

Dave

P.S.  I'm not saying that I like the names...

--
David J. C. Beach
Colorado State University
mailto:beach@verinet.com
http://www.verinet.com/~beach




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