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//
// CoreExtensions.Memoize.cs
//
// Author:
// Marius Ungureanu <maungu@microsoft.com>
//
// Copyright (c) 2019 Microsoft Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
using System;
using System.Collections.Generic;
namespace System
{
public static partial class CoreExtensions
{
public static Func<R> Memoize<R> (this Func<R> f)
{
R value = default;
bool hasValue = false;
return () => {
if (!hasValue) {
hasValue = true;
value = f ();
}
return value;
};
}
public static Func<T1, R> Memoize<T1, R> (this Func<T1, R> f)
{
var map = new Dictionary<T1, R> ();
return a => {
if (!map.TryGetValue (a, out R value)) {
map [a] = value = f (a);
}
return value;
};
}
public static Func<T1, R> MemoizeWithLock<T1, R> (this Func<T1, R> f)
{
var map = new Dictionary<T1, R> ();
return a => {
lock (map) {
if (!map.TryGetValue (a, out R value)) {
map[a] = value = f (a);
}
return value;
}
};
}
public static Func<T1, T2, R> Memoize<T1, T2, R> (this Func<T1, T2, R> f)
{
var map = new Dictionary<(T1, T2), R> ();
return (a, b) => {
var key = (a, b);
if (!map.TryGetValue (key, out R value)) {
map [key] = value = f (a, b);
}
return value;
};
}
public static Func<T1, T2, R> MemoizeWithLock<T1, T2, R> (this Func<T1, T2, R> f)
{
var map = new Dictionary<(T1, T2), R> ();
return (a, b) => {
var key = (a, b);
lock (map) {
if (!map.TryGetValue (key, out R value)) {
map [key] = value = f (a, b);
}
return value;
}
};
}
static class MemoizeUtil<Value>
{
public static Dictionary<Key, Value> Create<Key> (Key justForFancyTypeInference)
=> new Dictionary<Key, Value> ();
}
}
}
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