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fix: implement simple cache for pure functions
Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>
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// Copyright (c) 2023 IBM Corp. | ||
// All rights reserved. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License. | ||
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package function | ||
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import ( | ||
G "github.com/IBM/fp-go/function/generic" | ||
) | ||
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// Cache converts a unary function into a unary function that caches the value depending on the parameter | ||
func Cache[K comparable, T any](f func(K) T) func(K) T { | ||
return G.Cache(f) | ||
} | ||
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// ContramapCache converts a unary function into a unary function that caches the value depending on the parameter | ||
func ContramapCache[A any, K comparable, T any](kf func(A) K) func(func(A) T) func(A) T { | ||
return G.ContramapCache[func(A) T](kf) | ||
} |
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// Copyright (c) 2023 IBM Corp. | ||
// All rights reserved. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License. | ||
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package function | ||
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import ( | ||
"testing" | ||
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"github.com/stretchr/testify/assert" | ||
) | ||
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func TestCache(t *testing.T) { | ||
var count int | ||
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withSideEffect := func(n int) int { | ||
count++ | ||
return n | ||
} | ||
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cached := Cache(withSideEffect) | ||
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assert.Equal(t, 0, count) | ||
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assert.Equal(t, 10, cached(10)) | ||
assert.Equal(t, 1, count) | ||
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assert.Equal(t, 10, cached(10)) | ||
assert.Equal(t, 1, count) | ||
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assert.Equal(t, 20, cached(20)) | ||
assert.Equal(t, 2, count) | ||
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assert.Equal(t, 20, cached(20)) | ||
assert.Equal(t, 2, count) | ||
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assert.Equal(t, 10, cached(10)) | ||
assert.Equal(t, 2, count) | ||
} |
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// Copyright (c) 2023 IBM Corp. | ||
// All rights reserved. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License. | ||
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package generic | ||
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import ( | ||
"sync" | ||
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L "github.com/IBM/fp-go/internal/lazy" | ||
) | ||
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// Cache converts a unary function into a unary function that caches the value depending on the parameter | ||
func Cache[F ~func(K) T, K comparable, T any](f F) F { | ||
return ContramapCache[F](func(k K) K { return k })(f) | ||
} | ||
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// ContramapCache converts a unary function into a unary function that caches the value depending on the parameter | ||
func ContramapCache[F ~func(A) T, KF func(A) K, A any, K comparable, T any](kf KF) func(F) F { | ||
return CacheCallback[F](kf, getOrCreate[K, T]()) | ||
} | ||
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// getOrCreate is a naive implementation of a cache, without bounds | ||
func getOrCreate[K comparable, T any]() func(K, func() func() T) func() T { | ||
cache := make(map[K]func() T) | ||
var l sync.Mutex | ||
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return func(k K, cb func() func() T) func() T { | ||
// only lock to access a lazy accessor to the value | ||
l.Lock() | ||
existing, ok := cache[k] | ||
if !ok { | ||
existing = cb() | ||
cache[k] = existing | ||
} | ||
l.Unlock() | ||
// compute the value outside of the lock | ||
return existing | ||
} | ||
} | ||
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// CacheCallback converts a unary function into a unary function that caches the value depending on the parameter | ||
func CacheCallback[F ~func(A) T, KF func(A) K, C ~func(K, func() func() T) func() T, A any, K comparable, T any](kf KF, getOrCreate C) func(F) F { | ||
return func(f F) F { | ||
return func(a A) T { | ||
// cache entry | ||
return getOrCreate(kf(a), func() func() T { | ||
return L.Memoize[func() T](func() T { | ||
return f(a) | ||
}) | ||
})() | ||
} | ||
} | ||
} |
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// Copyright (c) 2023 IBM Corp. | ||
// All rights reserved. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License. | ||
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package lazy | ||
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import "sync" | ||
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// Memoize computes the value of the provided IO monad lazily but exactly once | ||
func Memoize[GA ~func() A, A any](ma GA) GA { | ||
// synchronization primitives | ||
var once sync.Once | ||
var result A | ||
// callback | ||
gen := func() { | ||
result = ma() | ||
} | ||
// returns our memoized wrapper | ||
return func() A { | ||
once.Do(gen) | ||
return result | ||
} | ||
} |
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