Question

In C# how do I memoize a function with two arguments?

Do I have to curry before memoization?

Wes Dyer wrote the Memoization code I typically use, but now I need two arguments

Answer 1

You just make an overloaded version of the Memoize method that has three generic types and takes a function with two parameters, and the two arguments. It still returns a parameterless function:

public static Func<R> Memoize<A1,A2,R>(this Func<A1,A2,R> f, A1 a1, A2 a2) {   R value = default(R);   bool hasValue = false;   return () =>     {       if (!hasValue)       {         hasValue = true;         value = f(a1,a2);       }       return value;     }; } 

Edit:
Alternatively, you need to make a custom IEqualityComparer for a KeyValuePair that contains the two arguments, for the Memoize method to be able to return a function with two parameters:

public static Func<A1,A2,R> Memoize<A1,A2,R>(this Func<A1,A2,R> f, IEqualityComparer<KeyValuePair<A1,A2>> comparer) {    var map = new Dictionary<KeyValuePair<A1,A2>,R>(comparer);    return (a1,a2) =>       {          R value;          KeyValuePair<A1,A2> key = new KeyValuePair<A1,A2>(a1,a2);          if (map.TryGetValue(key, out value)) {             return value;          }          value = f(a1,a2);          map.Add(key, value);          return value;       }; }