Questions about haskell CPP macros
Hello Cafe, I am trying to improve the error reporting in my sendfile library, and I know I can find out the current file name and line number with something like this: {-# LANGUAGE CPP #-} main = putStrLn (__FILE__ ++ ":" ++ show __LINE__) This outputs: test.hs:2 Unfortunately, if your file is in a hierarchy of folders, this flat file name doesn't give much context. Is there a macro to find out the current module? IE if I had a module Foo.Bar.Car.MyModule, I would like to be able to output something like this on error: Foo.Bar.Car.MyModule:2 Any help is appreciated! Thanks, Matt -- Need somewhere to put your code? http://patch-tag.com Want to build a webapp? http://happstack.com
I am trying to improve the error reporting in my sendfile library, and I know I can find out the current file name and line number with something like this:
{-# LANGUAGE CPP #-} main = putStrLn (__FILE__ ++ ":" ++ show __LINE__)
This outputs: test.hs:2
Unfortunately, if your file is in a hierarchy of folders, this flat file name doesn't give much context. Is there a macro to find out the current module? IE if I had a module Foo.Bar.Car.MyModule, I would like to be able to output something like this on error: Foo.Bar.Car.MyModule:2
Sounds like a job for cabal or ghc, to define appropriate macros for package and module when compiling the source?
Any help is appreciated!
For actually making use of such information, see http://hackage.haskell.org/trac/ghc/wiki/ExplicitCallStack http://hackage.haskell.org/trac/ghc/wiki/ExplicitCallStack/StackTraceExperie... and also the recent thread on how to improve the quality of "+RTS -xc" output via mapException (hmm, can't reach the archive at the moment, one subject was "Should exhaustiveness testing be on by default?", about May; http://www.haskell.org/mailman/listinfo/glasgow-haskell-users ). If you really mean "any help", you could also use Template Haskell:-) {-# LANGUAGE TemplateHaskell #-} module Oh.Hi where import Language.Haskell.TH main = print $( location >>= \(Loc f p m s e)-> stringE (f++":"++p++":"++m++":"++show s++":"++show e)) Claus
Matthew Elder wrote:
{-# LANGUAGE CPP #-} main = putStrLn (__FILE__ ++ ":" ++ show __LINE__)
This outputs: test.hs:2
Unfortunately, if your file is in a hierarchy of folders, this flat file name doesn't give much context. Is there a macro to find out the current module? IE if I had a module Foo.Bar.Car.MyModule, I would like to be able to output something like this on error: Foo.Bar.Car.MyModule:2
As mentioned by Claus, template-haskell offers a solution. But in some cases, this is an overkill; consider using Control.Exception.assert, it will provide module and line information without having to use CPP: myHead :: [a] -> a myHead (x:_) = x myHead [] = assert False undefined
[...]
//Stephan -- Früher hieß es ja: Ich denke, also bin ich. Heute weiß man: Es geht auch so. - Dieter Nuhr
{-# LANGUAGE CPP #-} main = putStrLn (__FILE__ ++ ":" ++ show __LINE__)
This outputs: test.hs:2
if I had a module Foo.Bar.Car.MyModule, I would like to be able to output something like this on error: Foo.Bar.Car.MyModule:2
It works for me. If you place that text in Try/Me.hs and call ghc -E Try/Me.hs you get Try/Me.hs:2 If you just want to turn slashes into dots, and remove the suffix, that is a simple exercise in Haskell itself main = putStrLn (mangle __FILE__) where mangle ('/':cs) = '.': mangle cs mangle ..... Regards, Malcolm
Malcolm Wallace wrote:
{-# LANGUAGE CPP #-} main = putStrLn (__FILE__ ++ ":" ++ show __LINE__)
This outputs: test.hs:2
if I had a module Foo.Bar.Car.MyModule, I would like to be able to output something like this on error: Foo.Bar.Car.MyModule:2
It works for me. If you place that text in Try/Me.hs and call ghc -E Try/Me.hs you get Try/Me.hs:2
If you just want to turn slashes into dots, and remove the suffix, that is a simple exercise in Haskell itself
main = putStrLn (mangle __FILE__) where mangle ('/':cs) = '.': mangle cs mangle .....
Careful, '/' might be '\\' on another OS, the file might end with .hsc instead of .hs, the line numbers might not fit in the .hsc case... -- Früher hieß es ja: Ich denke, also bin ich. Heute weiß man: Es geht auch so. - Dieter Nuhr
participants (4)
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Claus Reinke -
Malcolm Wallace -
Matthew Elder -
Stephan Friedrichs