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https://github.com/IBM/fp-go.git
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83 lines
2.1 KiB
Go
83 lines
2.1 KiB
Go
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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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FCT "github.com/ibm/fp-go/internal/functor/testing"
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"github.com/stretchr/testify/assert"
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)
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// Apply associative composition law
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//
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// F.ap(F.ap(F.map(fbc, bc => ab => a => bc(ab(a))), fab), fa) <-> F.ap(fbc, F.ap(fab, fa))
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func AssertAssociativeComposition[HKTA, HKTB, HKTC, HKTAB, HKTBC, HKTAC, HKTABAC, A, B, C any](t *testing.T,
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eq E.Eq[HKTC],
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fofab func(func(A) B) HKTAB,
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fofbc func(func(B) C) HKTBC,
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fmap func(HKTBC, func(func(B) C) func(func(A) B) func(A) C) HKTABAC,
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fapab func(HKTAB, HKTA) HKTB,
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fapbc func(HKTBC, HKTB) HKTC,
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fapac func(HKTAC, HKTA) HKTC,
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fapabac func(HKTABAC, HKTAB) HKTAC,
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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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fab := fofab(ab)
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fbc := fofbc(bc)
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left := fapac(fapabac(fmap(fbc, func(bc func(B) C) func(func(A) B) func(A) C {
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return func(ab func(A) B) func(A) C {
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return func(a A) C {
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return bc(ab(a))
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}
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}
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}), fab), fa)
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right := fapbc(fbc, fapab(fab, fa))
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return assert.True(t, eq.Equals(left, right), "Apply associative composition")
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}
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}
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// AssertLaws asserts the apply laws `identity`, `composition` and `associative composition`
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func AssertLaws[HKTA, HKTB, HKTC, HKTAB, HKTBC, HKTAC, HKTABAC, 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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fofab func(func(A) B) HKTAB,
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fofbc func(func(B) C) HKTBC,
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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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fmap func(HKTBC, func(func(B) C) func(func(A) B) func(A) C) HKTABAC,
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fapab func(HKTAB, HKTA) HKTB,
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fapbc func(HKTBC, HKTB) HKTC,
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fapac func(HKTAC, HKTA) HKTC,
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fapabac func(HKTABAC, HKTAB) HKTAC,
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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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// functor laws
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functor := FCT.AssertLaws(t, eqa, eqc, faa, fab, fac, fbc, ab, bc)
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// associative composition laws
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composition := AssertAssociativeComposition(t, eqc, fofab, fofbc, fmap, fapab, fapbc, fapac, fapabac, ab, bc)
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return func(fa HKTA) bool {
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return functor(fa) && composition(fa)
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}
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}
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