Donald Bruce Stewart wrote:
The following C program was described on #haskell
#include
int main() { double x = 1.0/3.0; double y = 3.0; int i = 1; for (; i<=1000000000; i++) { x = x*y/3.0; y = x*9.0; } printf("%f\n", x+y); }
Which was translated to the following Haskell:
{-# OPTIONS -fexcess-precision #-}
import Text.Printf
main = go (1/3) 3 1
go :: Double -> Double -> Int -> IO () go !x !y !i | i == 1000000000 = printf "%f\n" (x+y) | otherwise = go (x*y/3) (x*9) (i+1)
Do the two programs implement the same algorithm? The C program updates x and y in sequence. The Haskell program updates x and y in parallel and can be easier for the compiler to optimize.