[project @ 1998-01-30 16:57:33 by sof]

[ghc-hetmet.git] / ghc / lib / glaExts / NumExts.lhs

diff --git a/ghc/lib/glaExts/NumExts.lhs b/ghc/lib/glaExts/NumExts.lhs
new file mode 100644 (file)
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+++ b/ghc/lib/glaExts/NumExts.lhs
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+%
+% (c) The AQUA Project, Glasgow University, 1998
+%
+
+\section[NumExts]{Misc numeric bits}
+
+\begin{code}
+module NumExts
+
+       (
+         doubleToFloat   -- :: Double -> Float
+       , floatToDouble   -- :: Double -> Float
+       , showHex         -- :: Integral a => a -> ShowS
+       , showOct         -- :: Integral a => a -> ShowS
+       ) where
+
+import Char (ord, chr)
+import PrelBase (ord_0)
+import GlaExts
+\end{code}
+
+\begin{code}
+doubleToFloat :: Double -> Float
+doubleToFloat (D# d#) = F# (double2Float# d#)
+
+floatToDouble :: Float -> Double
+floatToDouble (F# f#) = D# (float2Double# f#)
+
+showIntAtBase :: Integral a => a -> (a -> Char) -> a -> ShowS
+showIntAtBase base toChr n r
+  | n < 0  = error ("NumExts.showIntAtBase: applied to negative number " ++ show n)
+  | otherwise = 
+    case quotRem n base of { (n', d) ->
+    case toChr d        of { C# c# -> -- stricter than necessary
+    let
+       r' = C# c# : r
+    in
+    if n' == 0 then r' else showIntAtBase base toChr n' r'
+    }}
+
+showHex :: Integral a => a -> ShowS
+showHex n r = 
+ showString "0x" $
+ showIntAtBase 16 (toChrHex) n r
+ where  
+  toChrHex d
+    | d < 10    = chr (ord_0   + fromIntegral d)
+    | otherwise = chr (ord 'a' + fromIntegral (d - 10))
+
+showOct :: Integral a => a -> ShowS
+showOct n r = 
+ showString "0o" $
+ showIntAtBase 8 (toChrOct) n r
+ where toChrOct d = chr (ord_0   + fromIntegral d)
+\end{code}