scala - Scalaz minimal imports required to inject right and left use -

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simple question, have looked @ 1 already: managing imports in scalaz7, can't figure out how minimally inject right , left methods objects construct instances of \/.

i did try:

import syntax.todataops , other variations of to... such syntax.toidops suggested in http://eed3si9n.com/learning-scalaz-day13.

simple example:

import scalaz.{\/, syntax} import // goes here  class test {      def returneithert(h: int): string \/ int = {         h right     } }

thanks, jason.

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i solved using import syntax.id._ i'm unsure why worked.

syntax.id contains syntax "plain" values, i.e. places no constraints on type of value.

in general, when import syntax expression of form x.op, place import syntax depends on type of x, because op needs valid operation on type.

because \/[a, b] universally quantified , b, using syntax x.left , x.right places no constraints on type of x. hence, belongs in syntax.id.

for working understanding of syntax available where, worth looking @ source of of modules make syntax packages. example, contrast idops[a], has syntax a, functorops[f[_],a], has requirement f functor.

i not sure name id comes exactly; perhaps related identity functor id, can defined type id[a] = a. if had choose type constraint values usable syntax.id, in id. being universally quantified in a, operations can't know structure of value of a, hence can't structure-altering operations on a.


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