1Result(3)                        OCaml library                       Result(3)
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NAME

6       Result - Result values.
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Module

9       Module   Result
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Documentation

12       Module Result
13        : sig end
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16       Result values.
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18       Result  values handle computation results and errors in an explicit and
19       declarative manner without resorting to exceptions.
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22       Since 4.08
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30   Results
31       type ('a, 'e) t = ('a, 'e) result =
32        | Ok of 'a
33        | Error of 'e
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36       The type for result values. Either a value Ok v or an error Error e .
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40       val ok : 'a -> ('a, 'e) result
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43       ok v is Ok v .
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47       val error : 'e -> ('a, 'e) result
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50       error e is Error e .
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54       val value : ('a, 'e) result -> default:'a -> 'a
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57       value r ~default is v if r is Ok v and default otherwise.
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61       val get_ok : ('a, 'e) result -> 'a
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64       get_ok r is v if r is Ok v and
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67       Raises Invalid_argument otherwise.
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71       val get_error : ('a, 'e) result -> 'e
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74       get_error r is e if r is Error e and
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77       Raises Invalid_argument otherwise.
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81       val bind : ('a, 'e) result -> ('a ->  ('b,  'e)  result)  ->  ('b,  'e)
82       result
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85       bind r f is f v if r is Ok v and r if r is Error _ .
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89       val join : (('a, 'e) result, 'e) result -> ('a, 'e) result
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92       join rr is r if rr is Ok r and rr if rr is Error _ .
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96       val map : ('a -> 'b) -> ('a, 'e) result -> ('b, 'e) result
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99       map f r is Ok (f v) if r is Ok v and r if r is Error _ .
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103       val map_error : ('e -> 'f) -> ('a, 'e) result -> ('a, 'f) result
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106       map_error f r is Error (f e) if r is Error e and r if r is Ok _ .
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110       val fold : ok:('a -> 'c) -> error:('e -> 'c) -> ('a, 'e) result -> 'c
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113       fold ~ok ~error r is ok v if r is Ok v and error e if r is Error e .
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117       val iter : ('a -> unit) -> ('a, 'e) result -> unit
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120       iter f r is f v if r is Ok v and () otherwise.
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124       val iter_error : ('e -> unit) -> ('a, 'e) result -> unit
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127       iter_error f r is f e if r is Error e and () otherwise.
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132   Predicates and comparisons
133       val is_ok : ('a, 'e) result -> bool
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136       is_ok r is true iff r is Ok _ .
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140       val is_error : ('a, 'e) result -> bool
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143       is_error r is true iff r is Error _ .
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147       val  equal  : ok:('a -> 'a -> bool) -> error:('e -> 'e -> bool) -> ('a,
148       'e) result -> ('a, 'e) result -> bool
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151       equal ~ok ~error r0 r1 tests equality of r0 and r1 using ok  and  error
152       to respectively compare values wrapped by Ok _ and Error _ .
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156       val  compare  : ok:('a -> 'a -> int) -> error:('e -> 'e -> int) -> ('a,
157       'e) result -> ('a, 'e) result -> int
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160       compare ~ok ~error r0 r1 totally orders r0 and r1 using ok and error to
161       respectively  compare values wrapped by Ok _ and Error _ .  Ok _ values
162       are smaller than Error _ values.
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167   Converting
168       val to_option : ('a, 'e) result -> 'a option
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171       to_option r is r as an option, mapping Ok v to Some v and  Error  _  to
172       None .
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176       val to_list : ('a, 'e) result -> 'a list
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179       to_list r is [v] if r is Ok v and [] otherwise.
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183       val to_seq : ('a, 'e) result -> 'a Seq.t
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186       to_seq r is r as a sequence.  Ok v is the singleton sequence containing
187       v and Error _ is the empty sequence.
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193OCamldoc                          2020-02-27                         Result(3)