Re: [racket-dev] Overly general types for mutable containers
On 07/07/2012 10:28 PM, Sam Tobin-Hochstadt wrote: On Sun, Jul 8, 2012 at 12:58 AM, Neil Toronto wrote: It runs directly counter to what I expect from immutable containers, which I use most of the time: This is the problem. Immutable containers are very different from mutable ones, and your expectations shouldn't be expected to carry over. Mutability is a communications channel, not just a data storage mechanism, and you should expect it to be different. Yes, I'm seeing that now. A lot. :D (I apologize for my recent negative tone. I've made up for it by submitting bug reports for you. Or something.) I keep trying to come up with better rules for generalizing the containee types in mutable containers. I haven't found any that don't have problems, so I'll have to be content with your choices on this. Neil ⊥ _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] redex.racket-lang.org Index of /
Eli: while you're at this, can you improve the watchdog script so that it would notice this? Robby On Sun, Jul 8, 2012 at 12:35 PM, David Van Horn wrote: > redex.racket-lang.org seems to have reverted to serving the index of /. > > David > _ > Racket Developers list: > http://lists.racket-lang.org/dev _ Racket Developers list: http://lists.racket-lang.org/dev
[racket-dev] redex.racket-lang.org Index of /
redex.racket-lang.org seems to have reverted to serving the index of /. David _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Custom write that pretty-prints and works well with quote?
Do `prop:custom-print-quotable' and/or `make-tentative-pretty-print-output-port' from `racket/pretty' help? At Sat, 07 Jul 2012 11:40:49 -0700, Neil Toronto wrote: > I've got an array structure like so: > > (struct: (A) strict-array ([shape : (Listof Index)] > [data : (Vectorof A)]) > > Say I have this value: > > (strict-array '(2 2) #(1 2 3 4)) > > I want it to print like this at the REPL: > > # > > If there's not enough room, I want this: > > #'(2 2) >'((1 2) (3 4))> > > If it happens to be in a list, I want this: > > (list #) > > and definitely NOT '(#) because the > inner quotes are confusing. > > How do I do that with prop:custom-write? The only way I've found so far > to get nicely formatted output is to write/display/print a list, but > then the quotes get messed up. I haven't found a way to keep the REPL > from quoting lists of structs, except to go with the default printer, > which flattens arrays, which makes them hard to read. > > This is frustrating. > > Neil ⊥ > _ > Racket Developers list: > http://lists.racket-lang.org/dev _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Proposal for a "no-argument"
Quick summary: I'll remove the #:before-first and #:after-last feature. If anyone wants them, please tell me -- maybe it can be left for the spliced case, or maybe they could always be spliced. On Monday, Matthew Flatt wrote: > I'm not enthusiastic about this proposal. > > As you say at the start, it seems like a rare case. My main > objection is that it's too rare to merit a change to the main > `lambda' form and other parts of our infrastructure, such as > documentation tools. This -- a more substantial extension of `lambda' and friends -- seems to be the core issue here. I've talked about it to Matthias, and we agreed on something that would help. I'll post about it separately, when I land. > As a weaker objection, I don't agree with the suggestion that naive > users can somehow ignore the `no-argument' value. I think it would show > up prominently in documentation, contracts, and types. I didn't mean that they'll ignore it -- I meant that having a default expression that is rendered as "no-argument" or something similar is self explanatory in a better way than "", and definitely from an additional #:nothing argument (which is an actual interface change in addition to being obscure). > Weaker still, in terms of how well I can defend it: I'm suspicious > of "no-value" values in general. Granted, we already have `#f', > #, and #, but I'm not really happy about that (and > I keep thinking about ways to get rid of #). This could be solved, roughly, by what both Robby and Matthias suggested (protecting it from leaking out), but on one hand there's a problem with that, and on the other it makes it equivalent to exposing a boolean flag for the presence of an argument. That's the thing that I'll delay for a proper post on that. Side-question: do you have some potential direction for eliminating #? (Asking because it might apply here too.) (Is there any problem with #?) Meanwhile, the interface change, the gensym-encouraging, and the obscurer explanation really bother me, so I'll just get rid of the need for them by removing the #:before-first and #:after-last feature. -- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life! _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Need a clarification on the implementation of stream-map
I'm not sure about the rationale behind the design of stream-map, but "any" as a result contract for a function indicates it may return multiple values (in the range of a function "any" is a special keyword). "any/c" is a contract for a single value. Robby On Sun, Jul 8, 2012 at 6:25 AM, Daniel King wrote: > Question 0: > > In collects/racket/stream.rkt, `stream-map' is defined as: > > (define (stream-map f s) > (unless (procedure? f) (raise-argument-error 'stream-map "procedure?" f)) > (unless (stream? s) (raise-argument-error 'stream-map "stream?" s)) > (let loop ([s s]) > (cond >[(stream-empty? s) empty-stream] >[else (stream-cons (call-with-values (lambda () (stream-first s)) f) > (loop (stream-rest s)))]))) > > > I don't understand the difference between: > > (call-with-values (lambda () (stream-first s)) f) > > and > > (f (stream-first s)) > > because the contract for `stream-first' is: > > (stream-first s) → any > s : (and/c stream? (not/c stream-empty?)) > > Which seems to me to just return a single value. I was taking a second look at > my changes to `stream-map' which add support for multiple streams. I noticed > this unusual snippet as I rebased onto the latest version of plt/master. > > > Question 1: > > Would it make more sense to simply update all the sequence procedures to > handle > multiple sequences? Is there a circumstance where it doesn't make sense to > handle multiple sequences in a sequence procedure such as `sequence-map'? > > I figure that the sequence procedures don't support multiple sequences is just > lack of interest. Do most people just use the `for' macros in these cases? > > -- > Dan King > College of Computer and Information Science > Northeastern University > > _ > Racket Developers list: > http://lists.racket-lang.org/dev _ Racket Developers list: http://lists.racket-lang.org/dev
[racket-dev] Need a clarification on the implementation of stream-map
Question 0: In collects/racket/stream.rkt, `stream-map' is defined as: (define (stream-map f s) (unless (procedure? f) (raise-argument-error 'stream-map "procedure?" f)) (unless (stream? s) (raise-argument-error 'stream-map "stream?" s)) (let loop ([s s]) (cond [(stream-empty? s) empty-stream] [else (stream-cons (call-with-values (lambda () (stream-first s)) f) (loop (stream-rest s)))]))) I don't understand the difference between: (call-with-values (lambda () (stream-first s)) f) and (f (stream-first s)) because the contract for `stream-first' is: (stream-first s) → any s : (and/c stream? (not/c stream-empty?)) Which seems to me to just return a single value. I was taking a second look at my changes to `stream-map' which add support for multiple streams. I noticed this unusual snippet as I rebased onto the latest version of plt/master. Question 1: Would it make more sense to simply update all the sequence procedures to handle multiple sequences? Is there a circumstance where it doesn't make sense to handle multiple sequences in a sequence procedure such as `sequence-map'? I figure that the sequence procedures don't support multiple sequences is just lack of interest. Do most people just use the `for' macros in these cases? -- Dan King College of Computer and Information Science Northeastern University _ Racket Developers list: http://lists.racket-lang.org/dev
