OK, all simply, show is not called if the term is considered not fully evaluated, which seems to be my case. So I'll need to write my own showTerm or maybe pprintClosureCommand, returning a String instead of just writing to standard out. Bypassing the isFullEvaluatedTerm condition gives me the expected result. Thanks, JP On Fri, Jan 24, 2014 at 7:09 PM, JP Moresmau wrote:

Karl, thanks, but the flag is set to True... And setting it to False doesn't change the output. I'll continue my investigations!

JP

On Fri, Jan 24, 2014 at 6:12 PM, Karl Voelker wrote:

...

On Fri, Jan 24, 2014, at 07:38 AM, JP Moresmau wrote:

Hello cafe, I'm continuing my adventures with the GHC API. I'm following the code given at http://www.haskell.org/haskellwiki/GHC/As_a_library#Running_interactive_stat... run statements like in GHCi, but the behavior sometimes puzzles me.

If I load a simple module:

module Test where import qualified Data.Text as T

And then run the statement T.pack \"test\", I expect to see "test" back. But I get Data.Text.Internal.Text _ 0 4. If I run "show $ T.Pack \"test\"" I get the expected result. Text _ 0 4 seems to be the output of the showText debugging function in Data.Text, that I don't see used in the Show instance. And looking at the GHC code (Debugger.hs) it does perform a show of the expression given. Why doesn't it work? What subtlety am I missing?

The example you linked to calls showTerm ( http://www.haskell.org/ghc/docs/latest/html/libraries/ghc/src/Debugger.html#...) which seems to have two different paths depending on the Opt_PrintEvldWithShow dynflag. One path appears to use show, and the other does not.

-Karl

-- JP Moresmau http://jpmoresmau.blogspot.com/

-- JP Moresmau http://jpmoresmau.blogspot.com/