[project @ 1997-05-18 04:04:30 by sof]

ghc/lib/required/Numeric.lhs

+%
+% (c) The AQUA Project, Glasgow University, 1997
+%
+\section[Numeric]{Numeric interface}
+
+Odds and ends, mostly functions for reading and showing
+\tr{RealFloat}-like kind of values.
+
+\begin{code}
+{-# OPTIONS -fno-implicit-prelude #-}
+module Numeric
+        (
+	 fromRat,
+	 showSigned, 
+	 readSigned, 
+	 showInt, 
+	 readInt,
+
+	 readDec, readOct, readHex,
+         showDec, showOct, showHex,
+
+	 showEFloat, 
+	 showFFloat, 
+	 showGFloat, 
+	 showFloat,
+	 readFloat, 
+	 
+	 floatToDigits,
+	 lexDigits
+
+	) where
+
+import PrelBase
+import ArrBase
+import PrelNum
+import PrelRead
+
+\end{code}
+
+%*********************************************************
+%*							*
+\subsection{Signatures}
+%*							*
+%*********************************************************
+
+Interface on offer:
+
+\begin{pseudocode}
+fromRat    :: (RealFloat a) => Rational -> a
+
+showSigned :: (Real a) => (a -> ShowS) -> Int -> a -> ShowS
+readSigned :: (Real a) => ReadS a -> ReadS a
+
+showInt    :: Integral a => a -> ShowS
+readInt    :: (Integral a) => a -> (Char -> Bool) -> (Char -> Int) -> ReadS a
+
+readDec    :: (Integral a) => ReadS a
+readOct    :: (Integral a) => ReadS a
+readHex    :: (Integral a) => ReadS a
+
+showEFloat    :: (RealFloat a) => Maybe Int -> a -> ShowS
+showFFloat    :: (RealFloat a) => Maybe Int -> a -> ShowS
+showGFloat    :: (RealFloat a) => Maybe Int -> a -> ShowS
+showFloat     :: (RealFloat a) => a -> ShowS
+ 
+readFloat      :: (RealFloat a) => ReadS a
+
+floatToDigits  :: (RealFloat a) => Integer -> a -> ([Int], Int)
+lexDigits      :: ReadS String
+\end{pseudocode}
+
+\begin{code}
+showInt :: Integral a => a -> ShowS
+showInt n r
+  = case quotRem n 10 of                 { (n', d) ->
+    case chr (ord_0 + fromIntegral d) of { C# c# -> -- stricter than necessary
+    let
+	r' = C# c# : r
+    in
+    if n' == 0 then r' else showInt n' r'
+    }}
+
+showIntAtBase :: Integral a => a -> (a -> Char) -> a -> ShowS
+showIntAtBase base toChr n r
+  = 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'
+    }}
+
+showDec :: Integral a => a -> ShowS
+showDec n r = 
+ showIntAtBase 10 
+               (\ d -> chr (ord_0 + fromIntegral d)) 
+	       n r
+
+showHex :: Integral a => a -> ShowS
+showHex n r = 
+ showString "0x" $
+ showIntAtBase 16 (toChrHex) n r
+ where  
+  toChrHex d = 
+   if d < 10 then
+      chr (ord_0   + fromIntegral d)
+   else
+      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}
+
+\begin{code}
+showEFloat    :: (RealFloat a) => Maybe Int -> a -> ShowS
+showFFloat    :: (RealFloat a) => Maybe Int -> a -> ShowS
+showGFloat    :: (RealFloat a) => Maybe Int -> a -> ShowS
+
+showEFloat d x =  showString (formatRealFloat FFExponent d x)
+showFFloat d x =  showString (formatRealFloat FFFixed d x)
+showGFloat d x =  showString (formatRealFloat FFGeneric d x)
+
+\end{code}
+      
+  
+