用VBS精确计算2的100次方的代码

'Date: 2010/10/27
'Author: Demon
'QQ: 380401911
'E-mail: still.demon@gmail.com

begin = Timer
n = 1
For i = 1 To 100
n = multiple(n, 2)
Next
finish = Timer
WScript.Echo n
WScript.Echo finish - begin

'Grade school multiplication, Algorithm 14.12
'http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf
Function multiple(byVal x, byVal y)
Dim n, t, i, j, z, w()
n = Len(x) - 1
t = Len(y) - 1
ReDim w(n + t + 1)

x = CStr(x) : y = CStr(y)

For i = 0 To UBound(w)
w(i) = "0"
Next

For i = 0 To t
Dim c : c = 0
Dim uv : uv = 0

For j = 0 To n
uv = (w(i+j)-"0") + c + _
(Mid(x,n-j+1,1)-"0") * (Mid(y,t-i+1,1)-"0")
w(i+j) = CStr(uv Mod 10 + "0")
c = uv / 10
Next

w(i+n+1) = CStr(uv / 10 + "0")
Next

z = Join(w,"")
z = StrReverse(z)
Do While Left(z,1) = "0"
z = Mid(z,2)
Loop

multiple = z
End Function