[Haskell-cafe] Recompiling Hackage to estimate the impact of a change [Was: StricterLabelledFieldSyntax]

Johan Tibell johan.tibell at gmail.com
Sun Jul 26 15:48:01 EDT 2009

On Sun, Jul 26, 2009 at 5:24 PM, Ian Lynagh <igloo at earth.li> wrote:

> On Sun, Jul 26, 2009 at 08:21:00AM +0200, Johan Tibell wrote:
> > On Sun, Jul 26, 2009 at 3:34 AM, Ian Lynagh <igloo at earth.li> wrote:
> >
> > >
> http://hackage.haskell.org/trac/haskell-prime/wiki/StricterLabelledFieldSyntax
> > >
> >
> > In general, I think it would be a good idea to provide some statistics of
> > how many packages would break as the result of a backwards incompatible
> > change. Without that data I find it hard to do a cost-benefit analysis.
> To some extent you are right, and if we had an easy to to get those
> stats when I would be in favour of doing so.
> But it is important to remember that a count of packages that break
> won't tell you how hard it would be to fix them. For example, the
> complete diff needed to fix old-time for StricterLabelledFieldSyntax
> was:
> -   toClockTime cal{ctMonth=month', ctYear=year'}
> +   toClockTime $ cal{ctMonth=month', ctYear=year'}

Right. So once you know what breaks you can investigate why and, as a part
of the language change proposal, show how easy/hard it would be to fix
breakages. I'm not arguing against breaking changes but for using the
available data to make decisions. For example, when a redesign of
haskell.org was brought up a while back the discussion could have greatly
benefited from looking at web server logs to give valuable insight into user
behavior on the site.

-- Johan
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