[project @ 1999-11-22 15:55:49 by simonmar]

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

diff --git a/ghc/lib/std/PrelRead.lhs b/ghc/lib/std/PrelRead.lhs
index 596b0c7..6c8da89 100644 (file)
--- a/ghc/lib/std/PrelRead.lhs
+++ b/ghc/lib/std/PrelRead.lhs
@@ -22,8 +22,8 @@ import PrelShow               -- isAlpha etc
 import PrelBase
 import Monad
 
--- needed for readIO.
-import PrelIOBase ( IO, userError )
+-- needed for readIO and instance Read Buffermode
+import PrelIOBase ( IO, userError, BufferMode(..) )
 import PrelException ( ioError )
 \end{code}
 
@@ -604,3 +604,26 @@ readRational__ top_s
 #endif
 
 \end{code}
+
+%*********************************************************
+%*                                                     *
+\subsection{Reading BufferMode}
+%*                                                     *
+%*********************************************************
+
+This instance decl is here rather than somewhere more appropriate in
+order that we can avoid both orphan-instance modules and recursive
+dependencies.
+
+\begin{code}
+instance Read BufferMode where
+    readsPrec _ = 
+      readParen False
+       (\r ->  let lr = lex r
+               in
+               [(NoBuffering, rest)       | ("NoBuffering", rest) <- lr] ++
+               [(LineBuffering,rest)      | ("LineBuffering",rest) <- lr] ++
+               [(BlockBuffering mb,rest2) | ("BlockBuffering",rest1) <- lr,
+                                            (mb, rest2) <- reads rest1])
+
+\end{code}