a few extensions for the itertools

[Mathias Panzenboeck]

Gabriel Genellina wrote:
 > At Sunday 19/11/2006 17:35, Mathias Panzenboeck wrote:
 >
 >> I wrote a few functions which IMHO are missing in python(s itertools).
 >>
 >> You can download them here:
 >> http://sourceforge.net/project/showfiles.php?group_id=165721&package_id=212104
 >>
 >>
 >> isum(iterable, start=0) -> value
 >>         Returns the sum of the elements of a iterable
 >>         plus the value of parameter 'start'.  When the
 >>         iterable is empty, returns start.
 >
 > Isn't the same as the builtin sum?
 >

No, because the builtin sum want's a list. This can also handle any kind of iterable, so this would 
work:

isum(i**2 for i in xrange(100))

sum would need firs the whole list to be generated:

sum([i**2 for i in xrange(100)])

 >> iproduct(iterable, start=0) -> value
 >
 > As others said, start should be 1
 >

Indeed. Can't believe I made that mistake... the mistake is only in the documentation. :)

 >> fcain(funct,*functs) -> function(...,***)
 >>         fcain(f1,f2,...,fn)(*args,*kwargs) equals
 >> f1(f2(...fn(*args,*kwargs)))
 >
 > I don't understand it, nor even the signature. Perhaps it tries to be
 > "fchain", function composition? But what has it to do with iterables?
 >

Ups, missed out the 'h'. (Also only in the documentation.)

It's like the . operator in haskell:

fchain(f,g,h) is the same like lambda *args,**kwargs: f(g(h(*args,**kwargs)))