[Haskell-cafe] Why is the Show instance of Text not used by showTerm?

JP Moresmau jpmoresmau at gmail.com
Fri Jan 24 15:38:02 UTC 2014

Hello cafe, I'm continuing my adventures with the GHC API. I'm following
the code given at
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?



JP Moresmau
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