[project @ 1997-03-24 08:39:18 by sof]

[ghc-hetmet.git] / ghc / lib / ghc / PrelRead.lhs

diff --git a/ghc/lib/ghc/PrelRead.lhs b/ghc/lib/ghc/PrelRead.lhs
index 6f3b8aa..f1f2b0b 100644 (file)
--- a/ghc/lib/ghc/PrelRead.lhs
+++ b/ghc/lib/ghc/PrelRead.lhs
@@ -11,7 +11,7 @@ The @Read@ class and many of its instances.
 
 module PrelRead where
 
-import {#- SOURCE #-}  IOBase  ( error )
+import {-# SOURCE #-}  IOBase  ( error )
 import PrelNum
 import PrelList
 import PrelTup
@@ -292,10 +292,12 @@ readRational :: ReadS Rational -- NB: doesn't handle leading "-"
 
 readRational r
   = [ ( (n%1)*10^^(k-d), t ) | (n,d,s) <- readFix r,
-                              (k,t)   <- readExp s]
+                              (k,t)   <- readExp s] ++
+    [(0/0, t) | ("NaN", t) <- lex r] ++
+    [(1/0, t) | ("Infinity", t) <- lex r]
               where readFix r = [(read (ds++ds'), length ds', t)
-                                       | (ds,'.':s) <- lexDigits r,
-                                         (ds',t)    <- lexDigits s ]
+                                       | (ds,s)  <- lexDigits r,
+                                         (ds',t) <- lexDotDigits s ]
 
                    readExp (e:s) | e `elem` "eE" = readExp' s
                     readExp s                    = [(0,s)]
@@ -304,6 +306,11 @@ readRational r
                     readExp' ('+':s) = readDec s
                     readExp' s      = readDec s
 
+                   lexDotDigits ('.':s) = lex0Digits s
+                   lexDotDigits s       = [("",s)]
+
+{- ToDo: remove completely
+
 readRational__ :: String -> Rational -- we export this one (non-std)
                                    -- NB: *does* handle a leading "-"
 readRational__ top_s
@@ -316,7 +323,7 @@ readRational__ top_s
          [x] -> x
          []  -> error ("readRational__: no parse:"        ++ top_s)
          _   -> error ("readRational__: ambiguous parse:" ++ top_s)
-
+-}
 -- The number of decimal digits m below is chosen to guarantee 
 -- read (show x) == x.  See
 --     Matula, D. W.  A formalization of floating-point numeric base
@@ -367,9 +374,9 @@ lex (c:s) | isSingle c = [([c],s)]
               isSym c    =  c `elem` "!@#$%&*+./<=>?\\^|:-~"
               isIdChar c =  isAlphanum c || c `elem` "_'"
 
-              lexFracExp ('.':s) = [('.':ds++e,u) | (ds,t) <- lexDigits s,
-                                                    (e,u)  <- lexExp t]
-              lexFracExp s       = [("",s)]
+              lexFracExp ('.':cs)   = [('.':ds++e,u) | (ds,t) <- lex0Digits cs,
+                                                       (e,u)  <- lexExp t]
+              lexFracExp s          = [("",s)]
 
               lexExp (e:s) | e `elem` "eE"
                        = [(e:c:ds,u) | (c:t)  <- [s], c `elem` "+-",
@@ -380,6 +387,10 @@ lex (c:s) | isSingle c = [([c],s)]
 lexDigits               :: ReadS String 
 lexDigits               =  nonnull isDigit
 
+-- 0 or more digits
+lex0Digits               :: ReadS String 
+lex0Digits  s            =  [span isDigit s]
+
 nonnull                 :: (Char -> Bool) -> ReadS String
 nonnull p s             =  [(cs,t) | (cs@(_:_),t) <- [span p s]]