On 22 March 2012 12:13, Simon Marlow wrote:

On 20/03/2012 20:12, Simon Hengel wrote:

...

They are now incremented with each evaluated expression.

Why *are* they incremented with each evaluation? Surely the only use for line numbers would be in multi-line statements:

:{ Prelude| do x <- [1..10] Prelude|    return y Prelude| :}

<interactive>:6:11: Not in scope: `y' Would it not make more sense to have <interactive>:2:11: Not in scope: `y' as it would do if compiling the file in a source file? From the older GHCs, this always gives 1, indicating that multi-line statements are somehow parsed and collapsed before being compiled, or maybe the line number was just hard coded to 1. FWIW, in my Emacs mode (making good progress on adding to haskell-mode) I use the column number in the REPL to highlight on the line where the problem is (e.g. here http://chrisdone.com/images/hs-repl-error-demo.png), for GHC 7.* with proper multi-line support I will automatically wrap any multi-line expressions entered in the REPL in :{ and :}, it would be cool for line numbers in errors to be useful for that. (Arguably we should be using the GHC API and Scion or something like it, but these change quite often and are hard to support whereas interfacing with GHCi is quite stable across around seven releases and "just works".)

...

ghc --interactive now behaves different in regards to line numbers in error messages than previous versions.

They are now incremented with each evaluated expression.

$ ghc --interactive -ignore-dot-ghci Prelude> foo

<interactive>:2:1: Not in scope: `foo' Prelude> bar

<interactive>:3:1: Not in scope: `bar'

Is there a way to disable this (or alternatively reset the counter for a running session)?

Sorry, there's no way to reset it at the moment. What do you need that for?

I use ghci for doctest [1] to evaluate examples. All examples within one Haddock comment are grouped to a /session/. And I reuse the same ghci process to run several sessions. Before a new session is run, I try (as far as possible) to reset ghci into a pristine state. The counter for line numbers is just one more thing that is carried over. A contrived example where this makes a difference is at [2]. I think this is not critical. But putting doctest aside, I still preferred the old behavior. Cheers, Simon [1] http://hackage.haskell.org/package/doctest [2] http://hpaste.org/65736