On Thu, Nov 26, 2009 at 02:43:14PM +0100, Fabrice Silva wrote:

Le jeudi 26 novembre 2009 à 18:26 +0200, Nadav Horesh a écrit :

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It is obvious to me that True+False == True,. Why do you think it should be False?

I would understand it is not obvious that '+' stands for logical 'or', and '*' for logical 'and'...

In Bool's algebra, this is the common convention. The reason being that only 'or' can correspond to the additive law of an algebra: its null element is absorbant for 'and'. In other words, if you map '+' and '*' to the opposite, you'll get suprising behaviors. Gaël

On Thu, 26 Nov 2009 15:14:04 +0100 Fabrice Silva wrote:

Le jeudi 26 novembre 2009 à 14:44 +0100, Gael Varoquaux a écrit :

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On Thu, Nov 26, 2009 at 02:43:14PM +0100, Fabrice Silva wrote:

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Le jeudi 26 novembre 2009 à 18:26 +0200, Nadav Horesh a écrit :

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It is obvious to me that True+False == True,. Why do you think it should be False?

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I would understand it is not obvious that '+' stands for logical 'or', and '*' for logical 'and'...

In Bool's algebra, this is the common convention. The reason being that only 'or' can correspond to the additive law of an algebra: its null element is absorbant for 'and'.

In other words, if you map '+' and '*' to the opposite, you'll get suprising behaviors.

I fully agree with you. My point was to complete Nadav's comment with potentially missing information, trying to figrue why Nils was expected False...

-- Fabrice Silva LMA UPR CNRS 7051

Sorry, I mixed up '+' and '&'

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a = array(([True,True],[True,True])) b = array(([False,False],[False,False])) a & b array([[False, False], [False, False]], dtype=bool)

Cheers, Nils