Re: [racket-dev] PLaneT Library of Iterations/Comprehensions
Dave, Thanks a bunch for pointing out the untyped code! I have a few questions below, mostly trying to understand the behavior of the macros and reconcile it with their names. I'm not sure that I understand for/foldl and friends. I think of the functions foldl (and foldr) as taking *one* accumulator, and filtering it through a function applied to each of the members of a sequence or sequences---that is, there are many function arguments, but only one accumulator. But, the foldl here looks like (define-syntax (for/foldl stx) (syntax-case stx () ((for/foldl accums (for-clause ...) body ...) (syntax/loc stx (call-with-values (lambda () (for/fold accums (for-clause ...) body ...)) (lambda args (car args))) That is, it has many accumulators, but returns only the first. (I tried defining the code you linked to at the REPL, and it barfed on some of the ...'s, so I wasn't able to test this assertion. I'm sure that I'm just missing some libraries.) Am I confused? This sounds more like for/fold/head, or for/fold/first, or something like that? I'm similarly a bit unhappy with the name for for/filter. The filter procedure takes a predicate, and removes any items from its list argument that don't satisfy the predicate. The for/filter macro is like a (hypothetical) for/lists, followed by a removal of the false elements. Is there possible a better name for this? How often do you find yourself using the multi-valued version (i.e. could we have a single-valued for/not-false or something, that gets most of the use cases)? I like for/append without reservation, and have added it to my local iteration branch, and I'll forward it to Sam once I've built the code and it passes some tests. Thanks again for suggesting these forms, Dave. Will On Aug 24, 2010, at 2:55 AM, Dave Gurnell wrote: > I use these guys all the time: > > http://github.com/untyped/unlib/blob/master/for.ss > > No guarantees that I'm not duplicating other peoples' efforts. > > Cheers, > > -- Dave > > On 22 Aug 2010, at 07:26, Noel Welsh wrote: > >> Hi Will, >> >> My "numerics" package on Github has for/vector with some slight >> extensions to yours. I think it also has more error checking so you >> might want to look at it. I also have for/fold/vector and some >> sequence abstractions. The code is all parameterised at expansion time >> by the vector representation. >> >> http://github.com/noelwelsh/numeric >> >> N. >> >> >> On Wed, Aug 18, 2010 at 5:02 PM, Will M. Farr wrote: >>> Hello all, >>> >>> I've been thinking for a while about putting together a PLaneT library of >>> some iteration/comprehension forms that I often use that are not found in >>> the racket core. Right now, I have a small it-comp.plt local PLaneT >>> package that contains >>> >>> for/vector >>> for/flvector >>> in-flvector >>> >>> The for/... forms have the option of having a first expression that gives >>> the length of the resulting object (similar to srfi-42's >>> vector-of-length-ec form) to allow generating more efficient code: >>> >>> (for/vector ((x (in-range 3))) x) => (vector 0 1 2) >>> (for/vector 3 ((x (in-range 3))) x) => (vector 0 1 2) ; but more efficiently >>> >>> I'll be adding more forms from time to time, as I need them. Eventually, >>> I'll release this to PLaneT, but I thought I might ask the community two >>> questions first: >>> >>> 1. Am I duplicating the functionality of some library? (If so, I'll just >>> contribute to that instead.) >>> 2. Do you have any iteration "favorites" that I should include in the >>> library? (Code welcome, but I'm also happy to implement suggestions >>> myself.) >>> >>> Alternately, if you guys want to add these to the core, I'd be happy to >>> contribute code and tests >>> >>> Thanks, >>> Will >>> _ >>> For list-related administrative tasks: >>> http://lists.racket-lang.org/listinfo/dev >>> >> _ >> For list-related administrative tasks: >> http://lists.racket-lang.org/listinfo/dev > > _ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] PLaneT Library of Iterations/Comprehensions
I use these guys all the time: http://github.com/untyped/unlib/blob/master/for.ss No guarantees that I'm not duplicating other peoples' efforts. Cheers, -- Dave On 22 Aug 2010, at 07:26, Noel Welsh wrote: > Hi Will, > > My "numerics" package on Github has for/vector with some slight > extensions to yours. I think it also has more error checking so you > might want to look at it. I also have for/fold/vector and some > sequence abstractions. The code is all parameterised at expansion time > by the vector representation. > > http://github.com/noelwelsh/numeric > > N. > > > On Wed, Aug 18, 2010 at 5:02 PM, Will M. Farr wrote: >> Hello all, >> >> I've been thinking for a while about putting together a PLaneT library of >> some iteration/comprehension forms that I often use that are not found in >> the racket core. Right now, I have a small it-comp.plt local PLaneT package >> that contains >> >> for/vector >> for/flvector >> in-flvector >> >> The for/... forms have the option of having a first expression that gives >> the length of the resulting object (similar to srfi-42's vector-of-length-ec >> form) to allow generating more efficient code: >> >> (for/vector ((x (in-range 3))) x) => (vector 0 1 2) >> (for/vector 3 ((x (in-range 3))) x) => (vector 0 1 2) ; but more efficiently >> >> I'll be adding more forms from time to time, as I need them. Eventually, >> I'll release this to PLaneT, but I thought I might ask the community two >> questions first: >> >> 1. Am I duplicating the functionality of some library? (If so, I'll just >> contribute to that instead.) >> 2. Do you have any iteration "favorites" that I should include in the >> library? (Code welcome, but I'm also happy to implement suggestions myself.) >> >> Alternately, if you guys want to add these to the core, I'd be happy to >> contribute code and tests >> >> Thanks, >> Will >> _ >> For list-related administrative tasks: >> http://lists.racket-lang.org/listinfo/dev >> > _ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] PLaneT Library of Iterations/Comprehensions
Hi Will, My "numerics" package on Github has for/vector with some slight extensions to yours. I think it also has more error checking so you might want to look at it. I also have for/fold/vector and some sequence abstractions. The code is all parameterised at expansion time by the vector representation. http://github.com/noelwelsh/numeric N. On Wed, Aug 18, 2010 at 5:02 PM, Will M. Farr wrote: > Hello all, > > I've been thinking for a while about putting together a PLaneT library of > some iteration/comprehension forms that I often use that are not found in the > racket core. Right now, I have a small it-comp.plt local PLaneT package that > contains > > for/vector > for/flvector > in-flvector > > The for/... forms have the option of having a first expression that gives the > length of the resulting object (similar to srfi-42's vector-of-length-ec > form) to allow generating more efficient code: > > (for/vector ((x (in-range 3))) x) => (vector 0 1 2) > (for/vector 3 ((x (in-range 3))) x) => (vector 0 1 2) ; but more efficiently > > I'll be adding more forms from time to time, as I need them. Eventually, > I'll release this to PLaneT, but I thought I might ask the community two > questions first: > > 1. Am I duplicating the functionality of some library? (If so, I'll just > contribute to that instead.) > 2. Do you have any iteration "favorites" that I should include in the > library? (Code welcome, but I'm also happy to implement suggestions myself.) > > Alternately, if you guys want to add these to the core, I'd be happy to > contribute code and tests > > Thanks, > Will > _ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev > _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] PLaneT Library of Iterations/Comprehensions
Sam, On Aug 18, 2010, at 1:39 PM, Sam Tobin-Hochstadt wrote: >> >> The for/... forms have the option of having a first expression that gives >> the length of the resulting object (similar to srfi-42's vector-of-length-ec >> form) to allow generating more efficient code: >> >> (for/vector ((x (in-range 3))) x) => (vector 0 1 2) >> (for/vector 3 ((x (in-range 3))) x) => (vector 0 1 2) ; but more efficiently > > What does this do if the specified length is wrong? If the length is too short, then there will be a vector access error with the correct syntax location (though it may be a bit cryptic); if the length is too long, then the returned vector will have some slots at the end that are undefined (i.e. filled with whatever (make-vector NN) produces). I think this kinda sucks, but I don't see any way to grab the length of a (for ...) form before it's run to check for consistency (in fact, I'm pretty sure you can't, since for loops can have #:while clauses that turn computation of the length into the halting problem). In my opinion, offering the fast path (the slow path makes a list first, then calls (list->vector ...) on the result, so the fast path should be a big win both in memory and speed) is worth the risk, but I'd be interested to hear what you think. I'm currently preparing the patch you requested; I'll let you know when it compiles and passes the tests on my system (which takes a while, since I have to build the whole racket environment). Will _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] PLaneT Library of Iterations/Comprehensions
On Wed, Aug 18, 2010 at 12:02 PM, Will M. Farr wrote: > Hello all, > > I've been thinking for a while about putting together a PLaneT library of > some iteration/comprehension forms that I often use that are not found in the > racket core. Right now, I have a small it-comp.plt local PLaneT package that > contains > > for/vector > for/flvector > in-flvector Great! > The for/... forms have the option of having a first expression that gives the > length of the resulting object (similar to srfi-42's vector-of-length-ec > form) to allow generating more efficient code: > > (for/vector ((x (in-range 3))) x) => (vector 0 1 2) > (for/vector 3 ((x (in-range 3))) x) => (vector 0 1 2) ; but more efficiently What does this do if the specified length is wrong? > Alternately, if you guys want to add these to the core, I'd be happy to > contribute code and tests If you prepare a patch (with tests/docs) I'll get it committed. -- sam th sa...@ccs.neu.edu _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
[racket-dev] PLaneT Library of Iterations/Comprehensions
Hello all, I've been thinking for a while about putting together a PLaneT library of some iteration/comprehension forms that I often use that are not found in the racket core. Right now, I have a small it-comp.plt local PLaneT package that contains for/vector for/flvector in-flvector The for/... forms have the option of having a first expression that gives the length of the resulting object (similar to srfi-42's vector-of-length-ec form) to allow generating more efficient code: (for/vector ((x (in-range 3))) x) => (vector 0 1 2) (for/vector 3 ((x (in-range 3))) x) => (vector 0 1 2) ; but more efficiently I'll be adding more forms from time to time, as I need them. Eventually, I'll release this to PLaneT, but I thought I might ask the community two questions first: 1. Am I duplicating the functionality of some library? (If so, I'll just contribute to that instead.) 2. Do you have any iteration "favorites" that I should include in the library? (Code welcome, but I'm also happy to implement suggestions myself.) Alternately, if you guys want to add these to the core, I'd be happy to contribute code and tests Thanks, Will _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
