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[project @ 2001-09-14 15:45:53 by simonpj]
author
simonpj
<unknown>
Fri, 14 Sep 2001 15:45:53 +0000
(15:45 +0000)
committer
simonpj
<unknown>
Fri, 14 Sep 2001 15:45:53 +0000
(15:45 +0000)
Add comments
ghc/lib/std/PrelFloat.lhs
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diff --git
a/ghc/lib/std/PrelFloat.lhs
b/ghc/lib/std/PrelFloat.lhs
index
ef065a4
..
be636ba
100644
(file)
--- a/
ghc/lib/std/PrelFloat.lhs
+++ b/
ghc/lib/std/PrelFloat.lhs
@@
-1,5
+1,5
@@
% ------------------------------------------------------------------------------
% ------------------------------------------------------------------------------
-% $Id: PrelFloat.lhs,v 1.12 2001/08/29 14:32:49 simonmar Exp $
+% $Id: PrelFloat.lhs,v 1.13 2001/09/14 15:45:53 simonpj Exp $
%
% (c) The University of Glasgow, 1994-2000
%
%
% (c) The University of Glasgow, 1994-2000
%
@@
-538,13
+538,18
@@
roundTo base d is =
(c,ds) = f (n-1) xs
i' = c + i
(c,ds) = f (n-1) xs
i' = c + i
---
-- Based on "Printing Floating-Point Numbers Quickly and Accurately"
-- by R.G. Burger and R.K. Dybvig in PLDI 96.
-- This version uses a much slower logarithm estimator. It should be improved.
-- Based on "Printing Floating-Point Numbers Quickly and Accurately"
-- by R.G. Burger and R.K. Dybvig in PLDI 96.
-- This version uses a much slower logarithm estimator. It should be improved.
--- This function returns a list of digits (Ints in [0..base-1]) and an
--- exponent.
+-- floatToDigits takes a base and a non-negative RealFloat number,
+-- and returns a list of digits and an exponent.
+-- In particular, if x>=0, and
+-- floatToDigits base x = ([d1,d2,...,dn], e)
+-- then
+-- (a) n >= 1
+-- (b) x = 0.d1d2...dn * (base**e)
+-- (c) 0 <= di <= base-1
floatToDigits :: (RealFloat a) => Integer -> a -> ([Int], Int)
floatToDigits _ 0 = ([0], 0)
floatToDigits :: (RealFloat a) => Integer -> a -> ([Int], Int)
floatToDigits _ 0 = ([0], 0)