1Option(3)                        OCaml library                       Option(3)
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NAME

6       Option - Option values.
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Module

9       Module   Option
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Documentation

12       Module Option
13        : sig end
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16       Option values.
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18       Option values explicitly indicate the presence or absence of a value.
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21       Since 4.08
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29   Options
30       type 'a t = 'a option =
31        | None
32        | Some of 'a
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35       The type for option values. Either None or a value Some v .
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39       val none : 'a option
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42       none is None .
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46       val some : 'a -> 'a option
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49       some v is Some v .
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53       val value : 'a option -> default:'a -> 'a
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56       value o ~default is v if o is Some v and default otherwise.
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60       val get : 'a option -> 'a
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63       get o is v if o is Some v and
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66       Raises Invalid_argument otherwise.
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70       val bind : 'a option -> ('a -> 'b option) -> 'b option
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73       bind o f is f v if o is Some v and None if o is None .
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77       val join : 'a option option -> 'a option
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80       join oo is Some v if oo is Some (Some v) and None otherwise.
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84       val map : ('a -> 'b) -> 'a option -> 'b option
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87       map f o is None if o is None and Some (f v) is o is Some v .
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91       val fold : none:'a -> some:('b -> 'a) -> 'b option -> 'a
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94       fold ~none ~some o is none if o is None and some v if o is Some v .
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98       val iter : ('a -> unit) -> 'a option -> unit
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101       iter f o is f v if o is Some v and () otherwise.
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106   Predicates and comparisons
107       val is_none : 'a option -> bool
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110       is_none o is true iff o is None .
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114       val is_some : 'a option -> bool
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117       is_some o is true iff o is Some o .
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121       val equal : ('a -> 'a -> bool) -> 'a option -> 'a option -> bool
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124       equal  eq o0 o1 is true iff o0 and o1 are both None or if they are Some
125       v0 and Some v1 and eq v0 v1 is true .
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129       val compare : ('a -> 'a -> int) -> 'a option -> 'a option -> int
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132       compare cmp o0 o1 is a total order on options using cmp to compare val‐
133       ues wrapped by Some _ .  None is smaller than Some _ values.
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138   Converting
139       val to_result : none:'e -> 'a option -> ('a, 'e) result
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142       to_result ~none o is Ok v if o is Some v and Error none otherwise.
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146       val to_list : 'a option -> 'a list
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149       to_list o is [] if o is None and [v] if o is Some v .
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153       val to_seq : 'a option -> 'a Seq.t
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156       to_seq  o is o as a sequence.  None is the empty sequence and Some v is
157       the singleton sequence containing v .
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163OCamldoc                          2021-01-26                         Option(3)