transformers 0.4: change in accessor function exports?

Ross Paterson R.Paterson at
Tue May 6 22:57:04 UTC 2014

On Wed, May 07, 2014 at 07:30:03AM +1000, Edward Kmett wrote:
> It may make the code in transformers a bit more confusing for a handful of
> instances, but this is breaking almost every user I've talked to.

My concern is not the implementation, it's the interface.

> This is proving to be a major breaking change as users commonly import StateT
> (..) and go off and use runStateT, etc.
> I wrote the imports in mtl 2.2 in such a way that if you recanted and chose to
> switch back to the old style, it'd still work.
> I just know that I personally have 200+ modules to change as a result, for no
> better experience as a user.

I'm convinced that this change is the right thing to do, but I haven't
managed it at all well.  So I'll do a minor release re-instating the
fields in short order, but still intend to remove them in the next major
release (with more preparation).

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