Question

I am trying a few problems (at Spoj) in Haskell and I have stumbled on quite a few which have input of the form:

testcase_1
testcase_1_continued
testcase_2 
testcase_2_continued

or

testcase_1 testcase_1_continued
...

As you can see, one cannot solve this by just using words or lines on the input and then mapping the solver function to get something like

[solver test1, solver test2, ...]

One should use a function with two arguements, which are two list elements, one after the other, and get:

[solver test1 test1continued, solver test2 test2continued, ...]

So I would be pleased to find an analogous function to map which applies a function 2 arguments at a time.I have not been able to find anything on Hoogle, and however easy it would be to write such a function, I am looking for a more general approach to the problem.Or, if my approach(of insisting on map) is definitely wrong, one could also point me to the right direction.

Edit:

I actually found it really useful to implement a function map2 which maps a function to a list, only it works two arguments a time:

map2 f [a,b,c,d] ==> [f a b, f c d]

Answer 1

Use chunksOf.

> map (\[x, y] -> x + y) . chunksOf 2 $ [1..30]
[3,7,11,15,19,23,27,31,35,39,43,47,51,55,59]