FAQ: How to Use Extensible Records in GHCi

[Alastair Reid]

> Is the feature described in the paper just a
> proposal or is there a switch somethere to enable
> it?

I think you used the wrong compiler.  It's called Hugs :-)

Prelude> #a ( a='a', b=True )
ERROR - Trex.insertField not in scope
*** Possible cause: "Trex" module not imported
Prelude> :l Trex
Trex> #a ( a='a', b=True )
'a'
Trex> #b ( a='a', b=True )
True

Documentation is here:

  http://cvs.haskell.org/Hugs/pages/hugsman/exts.html#sect7.2

--
Alastair Reid