如何比较列表中的两个元组？

Question

I have list of tuples like this:

[(0.0,0.0),(1.0,0.0),(2.0,0.0),(3.0,0.0),(3.0,0.0),(3.0,0.0),(4.0,0.0),(4.0,0.0)]

where first element is the X-coordinate and second the Y-coordinate and I now want to write function that will return :

[(0.0,0.0),(1.0,0.0),(2.0,0.0),(3.0,0.0),(3.0,1.0),(3.0,2.0),(4.0,0.0),(4.0,1.0)]

It takes first element from first tuple and first from second tuple and if they are not equal, Y is unchanged but if they are equal we add one to Y.

if someone has an idea how to write in Haskell?

Answer 1

Not tested, but something like this will do:

foo :: [(Float, Float)] -> [(Float, Float)]
foo []  = []
foo [x] = [x]
foo ((xx, xy):(yx, yy):xs) = (xx, xy): theTuple : (foo ((yx, yy):xs))
    where
        theTuple = if xx == yx then (yx, yy) else (yx, yy+1)