[Nix-dev] Haskell NG

[Charles Strahan]

> I'm trying to think of a way of selling my oop library [...]

What OOP library are you talking about? Is it available for me to view
online?

-Charles

On Thu, Dec 18, 2014 at 12:38 PM, <roconnor at theorem.ca> wrote:

> On Thu, 18 Dec 2014, Peter Simons wrote:
>
> > Hi Russel,
> >
> > >> 2) Haskell packages support 'deepOverride'.
> > >
> > > How would you feel about using my overrideScope functionality from my
> > > haskellPackagesFixpoint branch instead?
> >
> > the first version of my re-factored Haskell code defined deep overrides
> exactly
> > the way you did it. Check out the "definePackage" function in [1].
> You'll find
> > that I studied your work thoroughly.
> >
> > My impressions are:
> >
> > 1. overrideScope and deepOverride achieve the same goal. I discovered no
> case
> >    where one function worked but the other one didn't.
> >
> > 2. deepOverride is a standard function every callPackage derivation
> supports.
> >    overrideScope, on the other hand, is not.
> >
> > 3. deepOverride is implemented in a simple generic algorithm (for
> appropriate
> >    definitions of the term "simple") that requires no special support
> from the
> >    haskellPackages record to function. overrideScope, on the other hand,
> needs
> >    the magic nixClass attribute (__unfix__ in my code) to build a stack
> of
> >    extension functions.
> >
> > Ultimately, I felt that I should stick to the standard deepOverride
> mechanism
> > mostly due to Occam's razor'ish reasoning: I'd rather not introduce a new
> > sophisticated tying-the-knot mechanism to haskellPackages just to do the
> same
> > thing that deepOverride can do already.
> >
> > Does that make sense?
>
> That is fair reasoning.
>
> I will add that I expect overrideScope to run exponentially faster than
> deepOverride in worst case.  A similar change to replace-dependency took
> the evaluation time for replacing bash in a NixOS system from 65 minutes
> to instantaneous <https://githum.com/NixOS/nixpkgs/pull/4313>.  Replacing
> bash in a NixOS system is probably *the* worst case scenario because bash
> so deep in the dependency graph.  Until deepOverride starts taking
> appreciable time, the efficencies of overrideScope is probably not yet a
> pursuasive argument.
>
> So please keep an eye out for long evaluation times when using
> deepOverride as you continue your work. :)  Haskell applications have
> deeper and more fine grained dependencies than regular applications so
> you might be more likely to run into evaluation time problems than others.
>
> What I really need to do is convince Eelco Dolstra and Michael Raskin that
> semantics of overriding packages and semantics of object oriented
> programmed coincide and they should adopt my oop library for implementing
> the overriding mechanism.
>
> I'm trying to think of a way of selling my oop library to them that is a
> little more light weight that flying to europe to give them a presenation.
> Maybe I should use the Ocaml package set as a testbed to demonstrate
> overrideScope.
>
> --
> Russell O'Connor                                      <http://r6.ca/>
> ``All talk about `theft,''' the general counsel of the American Graphophone
> Company wrote, ``is the merest claptrap, for there exists no property in
> ideas musical, literary or artistic, except as defined by statute.''
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