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 raise otherwise.
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66       Raises Invalid_argument if o is None .
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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 if and only if o is None .
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114       val is_some : 'a option -> bool
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117       is_some o is true if and only if 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 if and only if o0 and o1 are both None or if
125       they are Some 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                          2023-01-23                         Option(3)