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[Python-Dev] Re: accumulator display syntax

Guido van Rossum guido at python.org
Wed Oct 22 22:48:40 EDT 2003 
> Thinking about the way this works in APL, where you can say things
> like
> 
>   total = + / numbers
> 
> one reason it's so compact is that the system knows what the identity
> is for each operator, so you don't have to specify the starting value
> explicitly. Another is the use of a binary operator.
> 
> So if we postulate a "reducing protocol" that requires function
> objects to have a __div__ method that performs reduction with a
> suitable identity, then we can write
> 
>    total = operator.add / numbers
> 
> Does that look succinct enough?

It still suffers from my main problem with reduce(), which is not its
verbosity (far from it) but that except for some special cases (mainly
sum and product) I have to stand on my head to understand what it
does.  This is even the case for examples like

  reduce(lambda x, y: x + y.foo, seq)

which is hardly the epitomy of complexity.  Who here knows for sure it
shouldn't rather be

  reduce(lambda x, y: x.foo + y, seq)

without going through an elaborate step-by-step execution?

This is inherent in the definition of reduce, and no / notation makes
it go away for me.

--Guido van Rossum (home page: http://www.python.org/~guido/)
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