From 6c8e740b5723f8904c81dbcec293dd288b377240 Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Mon, 1 Jul 2013 00:33:11 +0200
Subject: [PATCH] made parseBiggestFloat faster for large exponents

---
 lib/pure/parseutils.nim | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/pure/parseutils.nim b/lib/pure/parseutils.nim
index 989d45f475..1c543e6665 100644
--- a/lib/pure/parseutils.nim
+++ b/lib/pure/parseutils.nim
@@ -215,6 +215,17 @@ proc parseInt*(s: string, number: var int, start = 0): int {.
   else:
     number = int(res)
 
+proc tenToThePowerOf(b: int): biggestFloat =
+  var b = b
+  var a = 10.0
+  result = 1.0
+  while true:
+    if (b and 1) == 1:
+      result *= a
+    b = b shr 1
+    if b == 0: break
+    a *= a
+
 proc parseBiggestFloat*(s: string, number: var biggestFloat, start = 0): int {.
   rtl, extern: "npuParseBiggestFloat", noSideEffect.} =
   ## parses a float starting at `start` and stores the value into `number`.
@@ -280,9 +291,7 @@ proc parseBiggestFloat*(s: string, number: var biggestFloat, start = 0): int {.
       inc(i)
       while s[i] == '_': inc(i)
   # Calculate Exponent
-  var hd = 1.0
-  # XXX: this loop is horrible for large exponents:
-  for j in 1..exponent: hd = hd * 10.0
+  let hd = tenToThePowerOf(exponent)
   if esign > 0.0: number = number * hd
   else:           number = number / hd
   # evaluate sign