[Haskell-cafe] 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
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Re: [Haskell-cafe] Questions about haskell CPP macros
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/StackTraceExperience
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
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Re: [Haskell-cafe] Questions about haskell CPP macros
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
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Heute weiß man: Es geht auch so.
- Dieter Nuhr
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Re: [Haskell-cafe] Questions about haskell CPP macros
{-# 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
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Re: [Haskell-cafe] Questions about haskell CPP macros
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...
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Früher hieß es ja: Ich denke, also bin ich.
Heute weiß man: Es geht auch so.
- Dieter Nuhr
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