On Tue, Sep 18, 2007 at 02:26:38PM -0400, Olivier Boudry wrote:
Hi all,
I just tried the new GHCi debugger. A great new feature of GHCi 6.8.1.
When debugging a function, as for example the qsort function given as an example in the "3.5 The GHCi Debugger" documentation page, the debugger will only break on first function evaluation.
As haskell is pure and lazy it's probably a normal behavior (reuse last result instead of recompute) but it's not very practical in a debugger. I tried to reload (:r) but it doesn't seems to help. Is there a way to force the function to be re-evalutated without quitting, starting, loading prog and setting breakpoints again, other than making the function part of the IO monad. ;-)
There is a flag to do this, and it's even In The Manual! http://haskell.org/ghc/dist/current/docs/users_guide/ghci-set.html#id313085 3.8.1. GHCi options GHCi options may be set using :set and unset using :unset. The available GHCi options are: +r Normally, any evaluation of top-level expressions (otherwise known as CAFs or Constant Applicative Forms) in loaded modules is retained between evaluations. Turning on +r causes all evaluation of top-level expressions to be discarded after each evaluation (they are still retained during a single evaluation). This option may help if the evaluated top-level expressions are consuming large amounts of space, or if you need repeatable performance measurements. ... Stefan