Use explicit language extensions & remove extension fields from base.cabal

[ghc-base.git] / GHC / Float.lhs

diff --git a/GHC/Float.lhs b/GHC/Float.lhs
index aa2a534..02aba8c 100644 (file)
--- a/GHC/Float.lhs
+++ b/GHC/Float.lhs
@@ -1,9 +1,15 @@
 \begin{code}
-{-# OPTIONS_GHC -XNoImplicitPrelude #-}
+{-# LANGUAGE CPP
+           , NoImplicitPrelude
+           , MagicHash
+           , UnboxedTuples
+           , ForeignFunctionInterface
+  #-}
 -- We believe we could deorphan this module, by moving lots of things
 -- around, but we haven't got there yet:
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 {-# OPTIONS_HADDOCK hide #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.Float
@@ -600,7 +606,7 @@ floatToDigits base x =
    if e >= 0 then
     let be = expt b e in
     if f == expt b (p-1) then
-      (f*be*b*2, 2*b, be*b, b)
+      (f*be*b*2, 2*b, be*b, be)     -- according to Burger and Dybvig
     else
       (f*be*2, 2, be, be)
    else
@@ -785,11 +791,20 @@ expt base n =
     if base == 2 && n >= minExpt && n <= maxExpt then
         expts!n
     else
-        base^n
+        if base == 10 && n <= maxExpt10 then
+            expts10!n
+        else
+            base^n
 
 expts :: Array Int Integer
 expts = array (minExpt,maxExpt) [(n,2^n) | n <- [minExpt .. maxExpt]]
 
+maxExpt10 :: Int
+maxExpt10 = 324
+
+expts10 :: Array Int Integer
+expts10 = array (minExpt,maxExpt10) [(n,10^n) | n <- [minExpt .. maxExpt10]]
+
 -- Compute the (floor of the) log of i in base b.
 -- Simplest way would be just divide i by b until it's smaller then b, but that would
 -- be very slow!  We are just slightly more clever.