/// <summary>
/// Returns a Func<T,R> that wraps func. Each time the resulting
/// Func<T,R> is called with a new value, its result is memoized (cached).
/// Subsequent calls use the memoized value.
///
/// Remarks:
/// Thread-safe and memory-leak safe.
/// </summary>
public static Func <T, R> memo <T, R>(Func <T, R> func)
{
var cache = new WeakDict <T, R>();
var syncMap = new ConcurrentDictionary <T, object>();
return(inp =>
matchUnsafe(cache.TryGetValue(inp),
Some: x => x,
None: () =>
{
R res;
var sync = syncMap.GetOrAdd(inp, new object());
lock (sync)
{
res = cache.GetOrAdd(inp, func);
}
syncMap.TryRemove(inp, out sync);
return res;
}));
}
/// <summary>
/// Returns a `Func<A, B>` that wraps func. Each time the resulting
/// `Func<A, B>` is called with a new value, its result is memoized (cached).
/// Subsequent calls use the memoized value.
///
/// Remarks:
/// Thread-safe and memory-leak safe.
/// </summary>
public static Func <A, B> memo <A, B>(Func <A, B> func)
{
var cache = new WeakDict <A, B> ();
var syncMap = new ConcurrentDictionary <A, object>();
return(inp =>
{
if (cache.TryGetValue(inp, out var x))
{
return x;
}
else
{
B res;
var sync = syncMap.GetOrAdd(inp, new object());
lock (sync)
{
res = cache.GetOrAdd(inp, func);
}
syncMap.TryRemove(inp, out sync);
return res;
}
});
}
