{.experimental.}
import strutils,math,threadpool
import sequtils,macros,osproc

proc term(k: float): float = 4 * math.pow(-1, k) / (2*k + 1)
proc pi(n: int): float =
  var ch = newSeq[float](n+1)
  parallel:
    for k in 0..ch.high:
      ch[k] = spawn term(float(k))
  for k in 0..ch.high:
    result += ch[k]

let f = formatFloat(pi(5000))
echo f