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39 lines
1.3 KiB
Go
39 lines
1.3 KiB
Go
// Copyright (c) 2023 IBM Corp.
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// All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package option
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import (
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C "github.com/IBM/fp-go/constraints"
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F "github.com/IBM/fp-go/function"
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"github.com/IBM/fp-go/ord"
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)
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// Constructs an order for [Option]
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func Ord[A any](a ord.Ord[A]) ord.Ord[Option[A]] {
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// some convenient shortcuts
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fld := Fold(
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F.Constant(Fold(F.Constant(0), F.Constant1[A](-1))),
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F.Flow2(F.Curry2(a.Compare), F.Bind1st(Fold[A, int], F.Constant(1))),
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)
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// convert to an ordering predicate
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return ord.MakeOrd(F.Uncurry2(fld), Eq(ord.ToEq(a)).Equals)
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}
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// FromStrictCompare constructs an [Ord] from the canonical comparison function
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func FromStrictCompare[A C.Ordered]() ord.Ord[Option[A]] {
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return Ord(ord.FromStrictCompare[A]())
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}
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