Want to make a cache

Question

Here's the code for the problem I'm having. It's pretty simple but I'm still learning. I want to cache the result so the function returns a few seconds quicker than it currently is. At the moment it is returning to the caller in 4 when it should be 2.

Sub Main
    console.writeline(getmyresult(2)) 'takes a while'
    console.writeline(getmyresult(3)) 'takes a while'
    console.writeline(getmyresult(2)) 'Should be instant'
    console.writeline(getMyresult(3)) 'Should be instant'
End Sub


function getMyresult(X as interger) as integer
    dim Y as integer=LongCompute(X)
    return Y
end function


function LongCompute(X as integer) as integer
    system.threading.thread.sleep(1000)
    return x^2
end function

Any help would be greatly appreciated.

Answer 1

Yep, this is called memo-ization.

You can read up on it here: http://en.wikipedia.org/wiki/Memoization

A simple implementation in visual basic would look like:

Dim dict As New Dictionary(Of Integer, Integer)

Sub Main()
    console.writeline(getmyresult(2)) 'takes a while'
    console.writeline(getmyresult(3)) 'takes a while'
    console.writeline(getmyresult(2)) 'Should be instant'
    console.writeline(getMyresult(3)) 'Should be instant'
End Sub

Function getMyresult(ByVal X As Integer) As Integer
    If dict.ContainsKey(X) Then
        Return dict(X)
    Else
        Dim temp = LongCompute(X)
        dict.Add(X, temp)
        Return temp
    End If
End Function

Function LongCompute(ByVal X As Integer) As Integer
    System.Threading.Thread.Sleep(1000)
    Return x ^ 2
End Function