# Copyright 2011  Petter Urkedal
#
# This file is part of the Viz Standard Library <http://www.vizlang.org/>.
#
# The Viz Standard Library (VSL) is free software: you can redistribute it
# and/or modify it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 3 of the License,
# or (at your option) any later version.
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# more details.
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open prelude.ubiquitous

type t α := option α

val is_empty : option α → bool
val get : option α → α
val default : α → option α → α
val map : (α → β) → option α → option β
val fold : (α → β → β) → option α → β → β
val for_all : (α → bool) → option α → bool
val for_some : (α → bool) → option α → bool
val filter : (α → bool) → option α → option α
val flatten : option (option α) → option α

include prelude.option