Rationale for dropping List.scanl in elm 0.19

Learn
12

Basically, any use case of foldl where you also want the intermediate results.

If you want the sum of a list of numbers, you can write:

sum : List number -> number 
sum = List.foldl (+) 0

Substituting scanl gives you the cumulative sum, i.e. the list of intermediate sums:

cumulativeSum : List number -> List number 
cumulativeSum  = 
    scanl (+) 0


sum [1,2,3]
>> 6

cumulativeSum [1,2,3]
>> [0, 1, 3, 6]