[project @ 1998-02-02 17:27:26 by simonm]

[ghc-hetmet.git] / ghc / lib / std / Numeric.lhs

diff --git a/ghc/lib/std/Numeric.lhs b/ghc/lib/std/Numeric.lhs
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+%
+% (c) The AQUA Project, Glasgow University, 1997-98
+%
+\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,
+
+        showEFloat, 
+        showFFloat, 
+        showGFloat, 
+        showFloat,
+        readFloat, 
+        
+        floatToDigits,
+        lexDigits
+
+       ) where
+
+import PrelBase
+import PrelMaybe
+import PrelArr
+import PrelNum
+import PrelRead
+
+\end{code}
+
+%*********************************************************
+%*                                                      *
+\subsection[Numeric-signatures]{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'
+    }}
+\end{code}
+
+Controlling the format and precision of floats. The code that
+implements the formatting itself is in @PrelNum@ to avoid
+mutual module deps.
+
+\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}