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https://github.com/IBM/fp-go.git
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73 lines
2.0 KiB
Go
73 lines
2.0 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 testing
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import (
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"testing"
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E "github.com/IBM/fp-go/eq"
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F "github.com/IBM/fp-go/function"
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"github.com/stretchr/testify/assert"
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)
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// Functor identity law
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//
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// F.map(fa, a => a) <-> fa
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func AssertIdentity[HKTA, A any](t *testing.T, eq E.Eq[HKTA], fmap func(HKTA, func(A) A) HKTA) func(fa HKTA) bool {
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return func(fa HKTA) bool {
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return assert.True(t, eq.Equals(fa, fmap(fa, F.Identity[A])), "Functor identity law")
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}
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}
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// Functor composition law
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//
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// F.map(fa, a => bc(ab(a))) <-> F.map(F.map(fa, ab), bc)
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func AssertComposition[HKTA, HKTB, HKTC, A, B, C any](
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t *testing.T,
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eq E.Eq[HKTC],
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fab func(HKTA, func(A) B) HKTB,
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fac func(HKTA, func(A) C) HKTC,
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fbc func(HKTB, func(B) C) HKTC,
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ab func(A) B,
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bc func(B) C,
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) func(fa HKTA) bool {
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return func(fa HKTA) bool {
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return assert.True(t, eq.Equals(fac(fa, F.Flow2(ab, bc)), fbc(fab(fa, ab), bc)), "Functor composition law")
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}
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}
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// AssertLaws asserts the functor laws `identity` and `composition`
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func AssertLaws[HKTA, HKTB, HKTC, A, B, C any](t *testing.T,
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eqa E.Eq[HKTA],
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eqc E.Eq[HKTC],
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faa func(HKTA, func(A) A) HKTA,
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fab func(HKTA, func(A) B) HKTB,
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fac func(HKTA, func(A) C) HKTC,
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fbc func(HKTB, func(B) C) HKTC,
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ab func(A) B,
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bc func(B) C,
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) func(fa HKTA) bool {
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identity := AssertIdentity(t, eqa, faa)
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composition := AssertComposition(t, eqc, fab, fac, fbc, ab, bc)
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return func(fa HKTA) bool {
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return identity(fa) && composition(fa)
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}
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}
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