[Haskell-cafe] Newbie syntax question

Marc Ziegert coeus at gmx.de
Sat Sep 17 23:30:44 EDT 2005

> > map (foo 5) my_list_of_lists_of_doubles

> 1. map (flip foo 5) my_list_of_lists_of_doubles
> 2. map (`foo` 5) my_list_of_lists_of_doubles
> 3. map (\x->foo x 5) my_list_of_lists_of_doubles
> 4. [foo x 5 | x <- my_list_of_lists_of_doubles]

well, i've followed this discussion a while, but i did not see that solution i used for years. (i like solution 2, never thought of it before.)
my solution is a variant of 1, that makes the reading a little bit easier -- at least to me.

5. map (foo `flip` 5) my_list_of_lists_of_doubles

the `flip` shows the position behind foo, where to put the parameter. its a pitty that it only works if there is only one parameter behind `flip`.

so, with abcd :: a->b->c->d->x
abcd a b `flip` d :: c->x
works, but
abcd a `flip`  c d :: b->x
does not.

experimenting with Data.Arrow, it could look like:
(abcd a >>> ($ c) >>> ($ d)) :: b->x
or with a flip-arrow combination:
(abcd a `flip` c) >>> ($ d) :: b->x
so, instead of hacking with arrows on it, i prefer solutions 3 and 4 whenever 5 does not work.

- marc

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