haskell - Inconsistency between minimumBy and maximumBy -

when data.list.minimumby comes across list elements equal, chooses 1 came first, maximumby chooses last one:

> import data.list > import data.ord > minimumby (const (const eq)) "hello world!" 'h' > maximumby (const (const eq)) "hello world!" '!' 

is design or coincidence? there reasoning behind behavior?

note taking advantage of such assumption can make code more succinct - i.e minimumon length texts instead of using explicit tie-breaker such map snd (minimumon (\(p, t) -> (length t, p)) (zip [0..] texts))

in haskell report there comment min , max:

-- note (min x y, max x y) = (x,y) or (y,x)       max x y            | x <= y    =  y            | otherwise =  x       min x y            | x <= y    =  x            | otherwise =  y 

minimumby , maximumby using these or @ least trying stay consistent them.

i guess reason might use min , max to, say, write sort involved comparing , swapping pairs (as in operation in comment above). without property lose elements , have others duplicated.

you wouldn't able observe difference, since things compare equal identical. can imagine having elements sort of internal structure isn't considered comparisons not want lost during sort.