new python syntax: concatenation of functions

[Gonçalo Rodrigues]

On Thu, 11 Mar 2004 15:40:14 +0100, Curzio Basso
<curzio.basso at unibas.ch> wrote:

>Radovan Garabik wrote:
>
>> because neither in mathematics people agree on the order:
>> a°b(x) == a(b(x)) or
>> a°b(x) == b(a(x)) ?
>
>Is this a joke or what?
>
>In mathematics people DO agree on the order:
>
>if a:B->A and b:X->B, then a°b:X->A and
>(a°b)(x)=a(b(x))

No they DON'T. Both notations are used. The notation (using
concatenation instead of circle to denote composition)

ba: x -> a(b(x)) 

is called diagrammatic order, and to be totally consistent we should
really write

x -> (x b) a

and is more often used in Category Theory (and close relatives like
Homological Algebra, etc. ) where you deal more with commutative
diagrams and the like and functions being applied to arguments appear
only very rarely.

With my best regards,
G. Rodrigues