Why is there only 1 type parameter in scala list flatmap parameter signature -


why flatmap list takes b type parameter

def flatmap[b](f: (a) => u[b]): u[b]

instead of 

def flatmap[a, b](f: (a) => u[b]): u[b]

because a deduced type parameter defined on list:

sealed abstract class list[+a]

and since flatmap defined each element of type a in list, there's no need explicitly declare it.


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