import Math.Statistics.Fusion
import qualified Data.Vector.Unboxed as V
import Text.Printf
import Data.List

main = printf "%f\n" (mean (V.replicate 1000000000 (pi :: Double)))

{-
main = printf "%f\n" (mean (replicate 1000000000 (pi :: Double)))
    where
        mean x = fst $ foldl' (\(!m, !n) x -> (m+(x-m)/(n+1),n+1)) (0,0) x
-}

{-

Main_zdwfold_info:
.Lc122:
  movq %rdi,%rax
  cmpq $10000000,%rax
  jne .Lc126
  movq %rsi,%rbx
  jmp *(%rbp)
.Lc126:
  incq %rax
  leaq 1(%rsi),%rcx
  cvtsi2sdq %rsi,%xmm0
  movsd .Ln128(%rip),%xmm7
  subsd %xmm5,%xmm7
  divsd %xmm0,%xmm7
  addsd %xmm7,%xmm5
  movq %rcx,%rsi
  movq %rax,%rdi
  jmp Main_zdwfold_info

-}

{-
    -- ghc 6.12, vector package

Main_mainzuzdszdwfoldlMzuloop_info:
        testq   %r14, %r14
        jle     .L11
        movq    %rsi, %rdx
        movsd   .LC0(%rip), %xmm0
        cvtsi2sdq       %rdx, %xmm8
        leaq    -1(%r14), %r14
        subsd   %xmm5, %xmm0
        leaq    1(%rsi), %rsi
        divsd   %xmm8, %xmm0
        addsd   %xmm0, %xmm5
        jmp     Main_mainzuzdszdwfoldlMzuloop_info

-}