functional programming with map()

Luigi Ballabio ballabio at
Mon Feb 25 04:43:57 EST 2002

At 04:12 AM 2/25/02 +0000, Courageous wrote:

> >[x.f() for x in items]
>Yeah, whoever it was that decided this was the syntax
>for a list comprehension was just a plain genius. It's
>one of those linguistic thingies where you take one
>look at it, and you say, "of course".

It's from Haskell, I think, which in turn took it from plain old mathematics.
Haskell syntax is : [ f(x,y) | x <- items, y <- moreItems, x+y < 5  ]
Math notation is the same without brackets and with the "belongs to" symbol 
(the one you get with $\in$ in TeX). Well, you might have : instead of |, too.

Of course Guido might have travelled back in time and suggested it so that 
it was there for Python to borrow afterwards :)


More information about the Python-list mailing list