Factorial

[Jack]

QB64 has had _Shl and Shr for a while now, they are useful for quick multiply/divide by a power of 2, here'a factorial using only addition/subtraction and shifts
I can't think of a practical use for rol and ror

Code: (Select All)

Dim As _Integer64 N, b, c, p
Dim As Long i
For i = 0 To 20
    N = i
    c = N - 1
    p = 1
    While c > 0
        p = 0
        b = c
        While b > 0
            If b And 1 Then
                p = p + N
            End If
            b = _ShR(b, 1)
            N = _ShL(N, 1)
        Wend
        N = p
        c = c - 1
    Wend
    Print i; "! = "; p
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