Excellent point. I know exactly what is happening and am fixing it as we speak S | -----Original Message----- | From: Sean Seefried [mailto:seefried@itee.uq.edu.au] | Sent: 20 January 2003 05:28 | To: template-haskell@haskell.org | Subject: [Template-haskell] A subtle bug with GHC | | I've noticed a subtle bug with TH. It took me some time to realise what | was happening. First I will present my source files. | | --- [Splices.hs] ---- | module Splices where | | import Char | import Language.Haskell.THSyntax | | debug f = [| do { putStrLn (show ( $(f) + 3)) ; | putStrLn "Hello World!" } |] | | ---------------------------- | --- [ Main.hs] --------- | | module Main where | | import Language.Haskell.THSyntax | import Splices | | main = $(debug [| (1::Integer) |]) | ----------------------------- | | When I compile this from scratch using the command line: | | prompt> ghc --make -fglasgow-exts -package haskell-src -package | haskell98 Main.hs -o test | | we get | | prompt> | Chasing modules from: Main.hs | Compiling Splices ( Splices.hs, ./Splices.o ) | Compiling Main ( Main.hs, ./Main.o ) | Loading package base ... linking ... done. | Loading package haskell98 ... linking ... done. | Loading package haskell-src ... linking ... done. | Linking ... | | And the program works as expected. But I noticed that when I made a | small change to Main.hs and recompiled the following would occur: | | Skipping Splices ( Splices.hs, ./Splices.o ) | Compiling Main ( Main.hs, ./Main.o ) | Loading package base ... linking ... done. | Loading package haskell98 ... linking ... done. | Loading package haskell-src ... linking ... done. | | No instance for (Monad IO) | arising from a do statement at <compiler-generated-code> | In a right-hand side of function `main': | $[splice](debug [| (1 :: Integer) |]) | In the definition of `main': | main = $[splice](debug [| (1 :: Integer) |]) | make: *** [all] Error 1 | | | I can repeat this error at will. As long as Splices.hi and Splices.o | are in existence the above error will occur when trying to recompile | Main.hs. | | I was using ghc-5.05.20030118 | | Sean Seefried | | _______________________________________________ | template-haskell mailing list | template-haskell@haskell.org | http://www.haskell.org/mailman/listinfo/template-haskell