It might be reasonable to keep the patch for now in order not to introduce novel behavior this short before the 3.0 release.
But especially in light of Andy's work, I do regret introducing procedure-properties. It's a more LISPy feature than Schemey. Did you see Andy's argument about procedure equality below? I would have preferred to postpone the release and drop procedure equality, procedure-properties etc. It can be handy and convenient, yes, but there is a reason why R6RS didn't require (eq? p p) -> #t... Best regards, Mikael On Tue, Jan 14, 2020 at 5:37 PM Stefan Israelsson Tampe < stefan.ita...@gmail.com> wrote: > > > ---------- Forwarded message --------- > From: Stefan Israelsson Tampe <stefan.ita...@gmail.com> > Date: Tue, Jan 14, 2020 at 5:23 PM > Subject: Re: GNU Guile 2.9.9 Released [beta] > To: Mikael Djurfeldt <mik...@djurfeldt.com> > > > This is how it always have been in guile, without this patch you cannot > use procedure-property, use a function as a key to hash maps etc. If > this patch goes you need to forbid usage > of procedures as keys to hashmap, nuke procedure properties and friends or > mark it as internal to avoid luring schemers into using a faulty method. > This patch improves the use of higher order functions > not risk it. For example I often classify functions into different > categories and maintain this information as a property on the function via > a hashmap. This is a quite natural way of programming. Without it you need > to put the procedures in a datastructure and track that datastructure that > will uglify a lot of code. It is manageable but when the opposite is > similarly speeded code but much nicer and enjoyable code with absolutely no > risk in > higher order functionality countrary as you state (because higher order > worked flawlessly before in guile and the patch is restoring that). > > On Tue, Jan 14, 2020 at 5:07 PM Mikael Djurfeldt <mik...@djurfeldt.com> > wrote: > >> Hmm... it seems like both Stefan and you have interpreted my post exactly >> the opposite way compared to how it was meant. :) >> >> I completely agree that procedure equality is not strongly connected to >> the first citizen-ness. >> >> What I wanted to say is that I probably prefer you to *reverse* the >> recent patch because I prefer to have good optimization also when >> procedures are referenced by value in more than one non-operator position. >> I prefer this over having (eq? p p) => #t for the reasons I stated. >> >> Best regards, >> Mikael >> >> Den tis 14 jan. 2020 15:33Andy Wingo <wi...@pobox.com> skrev: >> >>> On Tue 14 Jan 2020 13:18, Mikael Djurfeldt <mik...@djurfeldt.com> >>> writes: >>> >>> > I probably don't have a clue about what you are talking about (or at >>> > least hope so), but this---the "eq change"---sounds scary to me. >>> > >>> > One of the *strengths* of Scheme is that procedures are first class >>> > citizens. As wonderfully show-cased in e.g. SICP this can be used to >>> > obtain expressive and concise programs, where procedures can occur >>> > many times as values outside operator position. >>> > >>> > I would certainly *not* want to trade in an important optimization >>> > step in those cases to obtain intuitive procedure equality. The risk >>> > is then that you would tend to avoid passing around procedures as >>> > values. >>> >>> Is this true? >>> >>> (eq? '() '()) >>> >>> What about this? >>> >>> (eq? '(a) '(a)) >>> >>> And yet, are datums not first-class values? What does being first-class >>> have to do with it? >>> >>> Does it matter whether it's eq? or eqv? >>> >>> What about: >>> >>> (eq? (lambda () 10) (lambda () 10)) >>> >>> What's the difference? >>> >>> What's the difference in the lambda calculus between "\x.f x" and "f"? >>> >>> What if in a partial evaluator, you see a `(eq? x y)`, and you notice >>> that `x' is bound to a lambda expression? Can you say anything about >>> the value of the expression? >>> >>> Does comparing procedures for equality mean anything at all? >>> https://cs-syd.eu/posts/2016-01-17-function-equality-in-haskell >>> >>> Anyway :) All that is a bit of trolling on my part. What I mean to say >>> is that instincts are tricky when it comes to object identity, equality, >>> equivalence, and especially all of those combined with procedures. The >>> R6RS (what can be more Schemely than a Scheme standard?) makes this >>> clear. >>> >>> All that said, with the recent patch, I believe that Guile 3.0's >>> behavior preserves your intuitions. Bug reports very welcome! >>> >>> Andy >>> >>
