Re: [racket-users] Macro guards question
> On May 29, 2019, at 11:09 AM, Sorawee Porncharoenwase > wrote: > > (foo a) ;=> 1 > (foo "a") ;=> 2 > (foo 10) ;=> 3 > (foo 'a) ;=> 4 > (foo (bar x)) ;=> 5 Ah… thanks so much for the explanation. That’s put me much closer (I hope!) to the solution I’m after. A bit of stumbling around through some documentation has got me this far.Being able to handle (foo a) and (foo b) below differently is a distinction I’ve been after for a while! #lang racket (define-syntax (foo stx) (syntax-case stx () [(_ arg) (and (identifier? #'arg) (identifier-binding #'arg 0 #t)) #'1] [(_ arg) (identifier? #'arg) #'2] [(_ arg) (string? (syntax->datum #'arg)) #'3] [(_ arg) (number? (syntax->datum #'arg)) #'4] [(_ (quote* x)) (and (free-identifier=? #'quote* #'quote) (symbol? (syntax->datum #'x))) #'5] [(_ _) #'6])) (define a #t) ;=> a is top-level bound, b is not. (foo a) ;=> 1 (foo b) ;=> 2 (foo "a") ;=> 3 (foo 10) ;=> 4 (foo 'a) ;=> 5 (foo (bar x)) ;=> 6 Kevin -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/506321EF-0D5B-4551-8671-268E6808B015%40gmail.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] anyone using single-flonums?
At Wed, 29 May 2019 12:33:24 -0400, George Neuner wrote: > Question: does/will Chez support converting to/from 32-bit floats for C > libraries? Yes. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/5ceeeb63.1c69fb81.1d6e7.1755SMTPIN_ADDED_MISSING%40gmr-mx.google.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] anyone using single-flonums?
I support them in various packages, but I rarely use them, per se. Those packages would have to be updated, but it wouldn't be a big deal for me. Doug On Wed, May 29, 2019 at 9:52 AM Matthew Flatt wrote: > Does anyone use single-flonums in Racket? > > I don't mean `_float` or `f32vector`s, which convert C `float`s or > 32-bit array elements into regular double-precision Racket flonums. I > mean literals like `3.0f0` or functions like `real->single-flonum`, > which produce a Racket number that uses only 32 bits for arithmetic. > > Chez Scheme doesn't support single-precision floating-point numbers, > and adding them would be a lot of work --- for no benefit, if it turns > out that no one is using those kinds of numbers. > > My guess is that no one uses them currently, because it's rare that > you'd want to trade speed for *im*precision. Single-flonums in Racket > are significantly slower than regular flonums, because they're not > treated as a common case. The only use I can think of, and the one that > inspired the original experiment, is to try to faithfully replicate a C > `float` calculation in Racket, but even that possibility has issues. > > If no one uses single-precision floats, then I will suggest that we > remove them from Racket by making numbers like `3.0f0` parse as flonums > and making `real->single-flonum` raise `exn:fail:unsupported`. > Obviously, this would be a backward-incompatible change. But if it > causes little enough trouble, then it could be a good trade to avoid > problems for Racket CS and future platforms. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/5ceeaac9.1c69fb81.118e3.f708SMTPIN_ADDED_MISSING%40gmr-mx.google.com > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CACvwowWy-q9Vr_GbBgxhRN9cQwGLk4ZO%3DsntG7yuwaRK%3D71oOA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] anyone using single-flonums?
My guess is that no one uses them currently, because it's rare that you'd want to trade speed for *im*precision. Single-flonums in Racket are significantly slower than regular flonums, because they're not treated as a common case. The only use I can think of, and the one that inspired the original experiment, is to try to faithfully replicate a C `float` calculation in Racket, but even that possibility has issues. To my knowledge, one reason to use single-precision numbers is that they occupy half as much memory, which is a big deal in e. g. video games and signal processing applications. No, I do not use them myself in Racket. Regards, Dmitry -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/cb9fe12e-5091-ec55-e542-73c19f8b7483%40iaaras.ru. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Macro guards question
The issue is that #'arg will always be a syntax object. An identifier is a kind of syntax object, so it makes sense to test (identifier? #’arg). However, (symbol? #’arg) and (string? #’arg) will always fail. Suppose then that you invoke the macro with "1" as the operand, it would fail every case in syntax-case, so syntax-case throws a bad syntax (because a syntax transformation must be total), causing the error that you saw. If you insist on using syntax-case, then try this: (define-syntax (foo stx) (syntax-case stx () [(_ arg) (identifier? #'arg) #'1] [(_ arg) (string? (syntax->datum #'arg)) #'2] [(_ arg) (number? (syntax->datum #'arg)) #'3] [(_ (quote* x)) (and (free-identifier=? #'quote* #'quote) (symbol? (syntax->datum #'x))) #'4] [(_ _) #'5])) (foo a) ;=> 1 (foo "a") ;=> 2 (foo 10) ;=> 3 (foo 'a) ;=> 4 (foo (bar x)) ;=> 5 A better way though is to use syntax-parse. (require (for-syntax syntax/parse)) (define-syntax (foo stx) (syntax-parse stx #:literals (quote) [(_ arg:id) #'1] [(_ arg:string) #'2] [(_ arg:number) #'3] [(_ (quote x:id)) #'4] [(_ _) #'5])) (foo a) ;=> 1 (foo "a") ;=> 2 (foo 10) ;=> 3 (foo 'a) ;=> 4 (foo (bar x)) ;=> 5 On Wed, May 29, 2019 at 10:23 AM Kevin Forchione wrote: > Hi Guys, > What are the rules for macro guards? I’ve only seen examples with > (identifier? #’val) being used. What about (number? #’val) or (spring? > #’val)? When I try these I get a foo: bad syntax so I’m suspecting these > can’t be used or there’s some trick to them. > > What I’ve been trying to create (and maybe this isn’t the right way to go > about it) is a syntax-case that would have have various type checks as > guards and then select the branch based on whether I’ve got an identifier > or just a symbol, or a number or a string, etc. > > (syntax-case six () > [(_ arg) (identifier? #’arg) #’(identifier-handler arg)] > [(_ arg) (symbol? #’arg) #’(symbol-handler arg)] > [(_ arg) (string? #’arg) #’(string-handler arg)] >…) > > That sort of thing. > > Primarily I find myself running into an issue where I’m using symbols for > lookup keys and identifiers for their reference values and running into a > wall of wanting the macro to go ahead and handle them differently without > have the old “foo undefined” popping up. :) > > Kevin > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/DED7E28E-9B3D-4045-B0DC-CBD3AB11E653%40gmail.com > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CADcuegvP%3DpmJRuZCSFmQjtyo7nxQFmo0JnoXjCW1WpnEdmnMpg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Macro guards question
#'arg is a syntax object, therefore (number? #'arg) or (string? #'arg) will always be false. If you are trying to dispatch based on literals, you could use e.g. (number? (syntax-e #'arg)) to identify a numeric literal. But it is not very common that a macro handles a numeric literal differently than an identifier that is bound to a numeric value at runtime. I'm guessing you can use a regular procedure and cond for most of this. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/111c1509-d77f-48d6-8c1f-19a37748cace%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] Macro guards question
Hi Guys, What are the rules for macro guards? I’ve only seen examples with (identifier? #’val) being used. What about (number? #’val) or (spring? #’val)? When I try these I get a foo: bad syntax so I’m suspecting these can’t be used or there’s some trick to them. What I’ve been trying to create (and maybe this isn’t the right way to go about it) is a syntax-case that would have have various type checks as guards and then select the branch based on whether I’ve got an identifier or just a symbol, or a number or a string, etc. (syntax-case six () [(_ arg) (identifier? #’arg) #’(identifier-handler arg)] [(_ arg) (symbol? #’arg) #’(symbol-handler arg)] [(_ arg) (string? #’arg) #’(string-handler arg)] …) That sort of thing. Primarily I find myself running into an issue where I’m using symbols for lookup keys and identifiers for their reference values and running into a wall of wanting the macro to go ahead and handle them differently without have the old “foo undefined” popping up. :) Kevin -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/DED7E28E-9B3D-4045-B0DC-CBD3AB11E653%40gmail.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] anyone using single-flonums?
On 5/29/2019 11:52 AM, Matthew Flatt wrote: Does anyone use single-flonums in Racket? I don't mean `_float` or `f32vector`s, which convert C `float`s or 32-bit array elements into regular double-precision Racket flonums. I mean literals like `3.0f0` or functions like `real->single-flonum`, which produce a Racket number that uses only 32 bits for arithmetic. Chez Scheme doesn't support single-precision floating-point numbers, and adding them would be a lot of work --- for no benefit, if it turns out that no one is using those kinds of numbers. My guess is that no one uses them currently, because it's rare that you'd want to trade speed for *im*precision. Single-flonums in Racket are significantly slower than regular flonums, because they're not treated as a common case. The only use I can think of, and the one that inspired the original experiment, is to try to faithfully replicate a C `float` calculation in Racket, but even that possibility has issues. If no one uses single-precision floats, then I will suggest that we remove them from Racket by making numbers like `3.0f0` parse as flonums and making `real->single-flonum` raise `exn:fail:unsupported`. Obviously, this would be a backward-incompatible change. But if it causes little enough trouble, then it could be a good trade to avoid problems for Racket CS and future platforms. Question: does/will Chez support converting to/from 32-bit floats for C libraries? It probably doesn't matter too much if Chez itself only *operates* on 64-bit values. But being able to pass 32-bit values I think is important. Machine learning is a hot topic now, and ANN often are implemented using matrix multiplication. A typical net involves a lot of mulitplications, so, at least on regular CPUs, it usually IS done with 32-bit for speed. [On some GPUs it is done with 16-bit FP values, and Google has an 8-bit FP chip. But no CPUs support these small FP values, and doing it with fixed point is a complex PITA (at least if you try to do it using SIMD ops)]. Aside: coming from a C/C++ image processing background, I've occasionally missed having SIMD ops native in Racket. FFI works fine, but calling out to a C library "feels" less natural [a bit like being forced to use intrinsics or drop into ASM in a C program]. It would be nice if Racket's array ops went SIMD at some point. YMMV, George -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/2e9df4a6-da50-7ac2-1bb5-2d0195a44b3a%40comcast.net. For more options, visit https://groups.google.com/d/optout.
[racket-users] anyone using single-flonums?
Does anyone use single-flonums in Racket? I don't mean `_float` or `f32vector`s, which convert C `float`s or 32-bit array elements into regular double-precision Racket flonums. I mean literals like `3.0f0` or functions like `real->single-flonum`, which produce a Racket number that uses only 32 bits for arithmetic. Chez Scheme doesn't support single-precision floating-point numbers, and adding them would be a lot of work --- for no benefit, if it turns out that no one is using those kinds of numbers. My guess is that no one uses them currently, because it's rare that you'd want to trade speed for *im*precision. Single-flonums in Racket are significantly slower than regular flonums, because they're not treated as a common case. The only use I can think of, and the one that inspired the original experiment, is to try to faithfully replicate a C `float` calculation in Racket, but even that possibility has issues. If no one uses single-precision floats, then I will suggest that we remove them from Racket by making numbers like `3.0f0` parse as flonums and making `real->single-flonum` raise `exn:fail:unsupported`. Obviously, this would be a backward-incompatible change. But if it causes little enough trouble, then it could be a good trade to avoid problems for Racket CS and future platforms. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/5ceeaac9.1c69fb81.118e3.f708SMTPIN_ADDED_MISSING%40gmr-mx.google.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] How to implement "APL" bitstrings in racket?
Hi, I would like to know how you would implement bitstrings "à la APL", meaning bitstrings/bitvectors of arbitrary dimensions with packed representation and possibilities for implicit parallelism. I am under the impression that this essentially means adding a bit type to the numeric tower, but I don't really know where to begin. Any suggestion would be welcome. I asked about bitstrings (valued 1|0) implementation in racket on Reddit already [1]. I received several suggestions among which: - mapping Boolean bitvectors to integer vectors (which means no packed representation) - or using the "rebellion" package, which implements packed bitstrings, but the implementation is partially imperative, making me worried about parallelism perspectives. Thanks! Raoul [1] https://www.reddit.com/r/Racket/comments/btrscb/can_true_bitvectors_be_implemented_in_racket/?utm_medium=android_app_source=share -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/911abf34-f5b7-4c96-9e5b-d40f51d5378f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
