Either - Either type.

Documentation

       Module Either
        : sigend

       Either type.

       Either  is  the simplest and most generic sum/variant type: a value of ('a,'b)Either.t is either a Left(v:'a) or a Right(v:'b) .

       It is a natural choice in the API of generic functions where values could fall in  two  different  cases,
       possibly at different types, without assigning a specific meaning to what each case should be.

       For example:

       List.partition_map:('a->('b,'c)Either.t)->'alist->'blist*'clist

       If  you  are  looking  for  a  parametrized  type where one alternative means success and the other means
       failure, you should use the more specific type Result.t .

       Since 4.12

       type('a,'b)t =
        | Left of'a
        | Right of'b

       A value of ('a,'b)Either.t contains either a value of 'a or a value of 'bvalleft : 'a->('a,'b)tleftv is Leftv .

       valright : 'b->('a,'b)trightv is Rightv .

       valis_left : ('a,'b)t->boolis_left(Leftv) is true , is_left(Rightv) is false .

       valis_right : ('a,'b)t->boolis_right(Leftv) is false , is_right(Rightv) is true .

       valfind_left : ('a,'b)t->'aoptionfind_left(Leftv) is Somev , find_left(Right_) is Nonevalfind_right : ('a,'b)t->'boptionfind_right(Rightv) is Somev , find_right(Left_) is Nonevalmap_left : ('a1->'a2)->('a1,'b)t->('a2,'b)tmap_leftfe is Left(fv) if e is Leftv and e if e is Right_ .

       valmap_right : ('b1->'b2)->('a,'b1)t->('a,'b2)tmap_rightfe is Right(fv) if e is Rightv and e if e is Left_ .

       valmap : left:('a1->'a2)->right:('b1->'b2)->('a1,'b1)t->('a2,'b2)tmap~left~right(Leftv) is Left(leftv) , map~left~right(Rightv) is Right(rightv) .

       valfold : left:('a->'c)->right:('b->'c)->('a,'b)t->'cfold~left~right(Leftv) is leftv , and fold~left~right(Rightv) is rightv .

       valiter : left:('a->unit)->right:('b->unit)->('a,'b)t->unititer~left~right(Leftv) is leftv , and iter~left~right(Rightv) is rightv .

       valfor_all : left:('a->bool)->right:('b->bool)->('a,'b)t->boolfor_all~left~right(Leftv) is leftv , and for_all~left~right(Rightv) is rightv .

       valequal : left:('a->'a->bool)->right:('b->'b->bool)->('a,'b)t->('a,'b)t->boolequal~left~righte0e1 tests equality of e0 and e1 using left and right to respectively compare  values
       wrapped by Left_ and Right_ .

       valcompare : left:('a->'a->int)->right:('b->'b->int)->('a,'b)t->('a,'b)t->intcompare~left~righte0e1 totally orders e0 and e1 using left and right to respectively compare values
       wrapped by Left_ and Right_ .  Left_ values are smaller than Right_ values.

OCamldoc                                           2025-06-12                                         Either(3o)