Merging two lists in Haskell

list haskell merge functional-programming interleave
bogatyrjov picture bogatyrjov · Oct 15, 2010 · Viewed 68.8k times · Source

Can't figure out how to merge two lists in the following way in Haskell:

INPUT:  [1,2,3,4,5] [11,12,13,14]

OUTPUT: [1,11,2,12,3,13,4,14,5]

Answer

Daniel picture Daniel · Oct 21, 2010

I want to propose a lazier version of merge:

merge [] ys = ys
merge (x:xs) ys = x:merge ys xs

For one example use case you can check a recent SO question about lazy generation of combinations.
The version in the accepted answer is unnecessarily strict in the second argument and that's what is improved here.

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