## VSL - The `data.free_monoid` Structure

# 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.
#
# The VSL is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
# more details.
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# You should have received a copy of the GNU Lesser General Public License
# along with the VSL. If not, see <http://www.gnu.org/licenses/>.
open prelude.ubiquitous
type t α := option (free_semigroup.t α)
let empty be none
let singleton x be some (free_semigroup.singleton x)
let length at none% be 0
at some a be free_semigroup.length a
let cat
at none% at b be b
at a at none% be a
at some a at some b be some (free_semigroup.cat a b)
let for_all f be option.for_all (free_semigroup.for_all f)
let for_some f be option.for_some (free_semigroup.for_some f)
let fold f be option.fold (free_semigroup.fold f)
let iter f be option.iter (free_semigroup.iter f)
let map f be option.map (free_semigroup.map f)
in tagged
let for_all f be option.for_all (free_semigroup.tagged.for_all f)
let for_some f be option.for_some (free_semigroup.tagged.for_some f)
let fold f be option.fold (free_semigroup.tagged.fold f)
let iter f be option.iter (free_semigroup.tagged.iter f)