Great application of "reassume"! =D I had to reinstall ATS2 to make the new
syntax available and now I've had a go at it.
can compile the "reassume"-example with [int2_t0ype] that you posted on
this list, so my reinstallation is working.
However, I don't seem to understand how to use "reassume" properly. If I
type
absvtype CSVErrors
local assume CSVErrors = List0_vt(CSVError) in (* nothing *) end
implement {CSVErrors} extfree(errs) =
let reassume CSVErrors
in case errs of
| ~list_vt_nil() => ()
| ~list_vt_cons(er, ers1) => extfree<CSVErrors>(ers1)
end
then I get an error saying "the identifier [CSVErrors] does not refer to a
static constant". Adding [vtypedef CSVErrors = CSVErrors] or
[stadef CSVErrors = CSVErrors] after the initial "absvtype" declaration
does not alleviate the problem. What's wrong?
Den tisdag 14 mars 2017 kl. 02:39:44 UTC+1 skrev gmhwxi:
>
>
> Please first do this:
>
> (*
> vtypedef
> CSVErrors = List0_vt(CSVError)
> *)
> absvtype CSVErrors
> local
> assume CSVErrors = List0_vt(CSVError)
> in (*nothing*) end
>
> Whenever you need the definition of CSVErrors, please do 'reassume
> CSVErrors' in the
> scope where you need it. For instance, I modified some of your code as
> follows:
>
> implement {} validate(rs: CSVTable): CSVResult =
> let
> reassume CSVErrors
> in
> $ldelay(
> case !rs of
> | ~nil() => let
> val nodata = list_vt_make_sing(No_Data()): CSVErrors
> in Left(nodata) :: empty()
> end
> | ~stream_vt_cons(r, rs1) => let
> val length_r = list_vt_length(r)
> implement {} current_length() = length_r
> in extract_errs(r) :: stream_vt_usermap(rs1, extract_errs)
> end
> ,
> ~rs
> )
> end
>
> After this, your code should be running, and hopefully, running correctly
> :)
>
>
>
>
> On Mon, Mar 13, 2017 at 9:09 PM, Hongwei Xi <gmh...@gmail.com
> <javascript:>> wrote:
>
> This is because CSVErrors is a dependent type.
>
> The right way to do it is to make CSVErrors abstract.
>
> If you are using ATS2-0.3.3, then you can use the feature of 'reassume'.
> I will show you how to do it in another message.
>
>
> On Mon, Mar 13, 2017 at 8:10 PM, August Alm <augu...@gmail.com
> <javascript:>> wrote:
>
> If I write
>
> implement extfree<CSVErrors> = ...
>
> then I get it passed the typechecking level of compilation, but when
> trying to generate C-code I instead get an error saying [extfree] has not
> been implemented:
>
> "csv_lexer_dats.c:93504:45: error: ‘extfree’ undeclared (first use in this
> function)"
>
>
>
> Den tisdag 14 mars 2017 kl. 00:57:18 UTC+1 skrev August Alm:
>
> Yes, as you guessed I am having problems with covariance. Some I have
> solved but this one leaves me very puzzled:
>
> I'll copy the code here in the order that it appears in my file. First (in
> "csv_lib.hats", which is #include:d at the very beginning) I have a template
>
> extern fun {a: vt0ype} extfree(x: a): void
>
> which is used to free variables in some of the functions using the
> [Either] constructor. Then I have:
>
> vtypedef CSVErrors = List0_vt(CSVError)
>
> where CSVError is a non-linear datatype. If I after that definition write
>
> implement {CSVErrors} extfree(errs) = list_vt_free(errs),
>
> then I get a compiler error telling me that [CSVErrors] can't be assigned
> the type of linear lists. If I try to go explicit and write
>
> implement{CSVErrors} extfree(errs) = let
> val errs: List0_vt(CSVError) = errs
> in case errs of
> | ~list_vt_nil() => ()
> | ~list_vt_cons(er, ers1) => extfree<CSVErrors>(ers1)
> end
>
> then I get roughly the same error, saying:
>
> The actual term is: S2Evar(CSVErrors(8927))
> The needed term is: S2Eapp(S2Ecst(list_vt0ype_int_vtype);
> S2Ecst(CSVError), S2EVar(5476))
>
> How can I help the compiler infer that CSVErrors is indeed a
> listvt0ype_int_vtype of CSVError?
>
> Den måndag 13 mars 2017 kl. 23:42:03 UTC+1 skrev gmhwxi:
>
> Once INV annotation is done properly, template annotation can be pretty
> much removed.
>
>
> On Mon, Mar 13, 2017 at 6:39 PM, August Alm <augu...@gmail.com> wrote:
>
> Thanks for the hint! I added template arguments wherever I could and now I
> got some error messages that actually say something. However, I do find it
> a bit disconcerting that the compiler would segfault rather than tell me I
> need to annotate templates.
>
> Den måndag 13 mars 2017 kl. 22:02:57 UTC+1 skrev gmhwxi:
>
> I will take a look later. Based on your description, the issue
> seems to be caused by not providing certain template arguments
> explicitly:
>
> Say, foo is a template. Please use foo<...>(...) instead of foo(...)
>
> Compared to Haskell, type inference in ATS is quite limited :)
>
> On Mon, Mar 13, 2017 at 4:51 PM, August Alm <augu...@gmail.com> wrote:
>
> So... I added some "second stage" parsing functionality, to get the en
> result in tabular form rahter than as a single [stream_vt], and to check
> for global errors such as unequal number of columns in the rows, and now I
> am back to segfaulting! =( However, this time it does not seem to be a
> stack issue because I run into the segmentation fault already at the
> compilation stage.
>
> I code in Vim and have it set up so that typing ":make" will run "patsopt
> -tc -d %", i.e., typechecking only. When I do everything seems fine--no
> complaints. I have used this utility for some time now and it has always
> worked like a charm. Wierdly though, if I issue "$ patsopt -tc -d
> csv_lexer.dats" in the console instead I get a segfault. The same happens
> for every other compilation command: I've tried compiling just using type
> checking, just to c, or etc. Always segfault. Compiling with the "-verbose"
> flag prints
>
> exec(patsopt --output csv_lexer_dats.c --dynamic csv_lexer.dats)
> Segmentation fault
> exec(patsopt --output csv_lexer_dats.c --dynamic csv_lexer.dats) = 35584
>
> which does not tell me anything.
>
> My code can be found at https://github.com/August-Alm/ats_csv_lexer Note
> that I have moved some function implementations into a hats-file. Might
> this be a cause of trouble? Any tips at all on how to debug this are most
> appreciated. I don't know where to even begin as gdb seems useless as long
> as I can't even generate the C-code.
>
> Best wishes,
> August
>
> Den onsdag 8 mars 2017 kl. 23:44:10 UTC+1 skrev gmhwxi:
>
> >>I take that as being somewhat tongue-in-cheek. ATS is a very theoretical
> language, after all.
>
> I know that this sounds very ironic but interesting stuff often does sound
> ironic :)
>
> My view of programming language research is changing gradually but surely.
> I now strongly feel
> that the most important programming support is to facilitate the need to
> alter/adapt the behaviour
> of a written program without actually requiring direct changes to be made
> to the program. And the
> template system of ATS can be seen as an attempt to provide programming
> support of this sort.
>
>
> On Wed, Mar 8, 2017 at 4:47 PM, August Alm <augu...@gmail.com> wrote:
>
> See in.
>
> Den onsdag 8 mars 2017 kl. 17:51:36 UTC+1 skrev gmhwxi:
>
> Tangential to the topic of monads: Do you know if someone has thought
> about the relations between ATS and "enriched effect calculus" (as
> described in http://homepages.inf.ed.ac.uk/als/Research/Sources/eec.pdf)
> or "linear state monads" (as mentioned in
> https://arxiv.org/pdf/1403.1477.pdf)? There is a clear analogy.
> Implementing a concept such as a linear state monad in ATS would be nice, I
> think. Monadic programming on an Arduino, anyone? =) It would certainly be
> a unique selling point.
>
>
> I can't really follow these monad papers. Too much for me :)
> Given your background, maybe you could give this a try?
>
> I'm tempted but I feel like I have to understand ATS:s function tags
> ("cloref" and the like, the flavours of function) better first, and
> generally get a more solid footing. I don't want to write something "cool",
> I want it to be useful, too.
>
>
> Over the years, I have gradually grown more and more cynic about
> "theoretic" research
> in the area of programming languages. I feel that the most urgent issue in
> programming is
> to find effective approaches to reducing programming complexity.
>
> I take that as being somewhat tongue-in-cheek. ATS is a very theoretical
> language, after all. To clarify, I think Haskell suffers greatly from
> having too little focus on efficiency (among many of its users, not among
> the guys working on the compiler). I heard about ATS about the same time as
> I heard about Idris (the dependent type thing) and decided to pursue ATS
> precisely because of its air of efficiency and "real-world-readiness". I do
> still love my Haskell though, mainly because it is so easy to be productive
> with it. Scala has a very good no-bs culture and good library hygiene, but
> I'm not too fond of OOP so...
>
>
> For instance, in your csv parser, there are a lot of if-then-else's. Maybe
> you took them from
> some Haskel code. The point is that if-then-else's make programming hard
> to write and harder
> to read/follow. I propose the following style:
>
> I first tried to write it using only pattern matching but failed to get it
> passed the typechecker. Maybe I will have another go at it.
>
>
> 1) Implementing a csv parser without worrying about quotes (DQUOT). Call
> this version 1.
> 2) Using templates to improve version 1 without directly modifying version
> 1. Another way
> to put it: you still have version 1 available after doing the
> improvement.
>
> If I was uncertain about the algorithm then such an incremental
> development style would surely be preferable, but since the code is a port
> of a tried and tested Haskell library I'm
> not very motivated to scrap and start over. But for my next project(s) I
> will try to heed your words.
>
> I know that this may sound a bit vague but that is my point. Being vague
> makes people
> think more and more deeply :)
>
> Cheers!
>
>
> On Tuesday, March 7, 2017 at 4:52:58 PM UTC-5, August Alm wrote:
>
> I'm glad too! I wrote my first "Hello World" program (in Haskell) less
> than four months ago, before that I was completely illiterate about
> programming--writing a linear, lazy CSV-parser in ATS has definitely been
> my most challenging venture so far. I mean this in a good way. ATS is
> quickly becoming my favorite language. It is daunting at times, sure, but
> its unique combination of low-level abilities and functional abstractions
> makes me feel like the Star Trek idiom "To boldly go where no one has gone
> before", heh. The ATS sky is so vast I've almost forgot about monads. And
> YES!, I do suggest trying ATS to every programmer I meet.
>
> Tangential to the topic of monads: Do you know if someone has thought
> about the relations between ATS and "enriched effect calculus" (as
> described in http://homepages.inf.ed.ac.uk/als/Research/Sources/eec.pdf)
> or "linear state monads" (as mentioned in
> https://arxiv.org/pdf/1403.1477.pdf)? There is a clear analogy.
> Implementing a concept such as a linear state monad in ATS would be nice, I
> think. Monadic programming on an Arduino, anyone? =) It would certainly be
> a unique selling point.
>
> I do not understand what you're aiming at with your suggestion to maje
> CSVState a datavtype or absvtype. Could you elaborate? I have seen abstract
> types used as a way to make otherwise allowed operation illegal (there is
> an example in your book, I think, of how to construct a record type where
> some fields are mutable and some are not), but not for the sake of
> overloading symbols.
>
> I will rewrite the code so that DELIM and QNLIN are passed as templates. I
> also intend to add some further functionality, like functions for filtering
> out errors, for printing and for collecting the output in tabular form with
> rows and columns rather than as a single row. When I'm satisfied I will
> make an npm-package out of it.
>
> Best wishes,
> August
>
> Den tisdag 7 mars 2017 kl. 02:21:00 UTC+1 skrev gmhwxi:
>
> Really glad that you got it to work!
>
> I suggest that you make a npm-package for the parser and then
> publish the package. In this way, other ats-lang users can benefit
> from your work easily.
>
> You could try to introduce some abstract types into your code. For
> instance, I would suggest that you make CSVstate a datavtype (linear
> datatype)
> (a datatype is often referred to as being semi-abstract). Then you can
> introduce overloaded symbols for functions processing CSVstate, making
> your code
> more accessible.
>
> Also, the following interface:
>
> extern fun
> lex_csv(QNLIN: bool, DELIM: char, cs: llstring): CSVEntries
>
> can and probably should be changed into
>
> extern
> fun{}
> lex_csv(cs: listing): CSVEntries
>
> The parameters QNLIN and DELIM can be passed via templates:
>
> extern
> fun{} lex_csv$QNLIN(): char
> extern
> fun{} lex_csv$DELIM(): char
>
> implement{} lex_csv$QNLIN() = false
> implement{} lex_csv$DELIM() = ',' // default value
>
> Writing function templates (instead of functions) enables you to move
> your code around very conveniently. You can even move template code
> into the body of another function.
>
> That's all for now. Hope you will like ATS and tell/teach it to your
> friends.
>
> Cheers!
>
> On Monday, March 6, 2017 at 4:06:11 PM UTC-5, August Alm wrote:
>
> The code now seems to work as inteded!
>
> https://github.com/August-Alm/ats_csv_lexer
>
> Thank you for all the help. I still don't fully grokk why the function
> needs to consume each of its arguments--will have to meditate more on
> that--but at least I know how to write code like this from now on.
>
> Den måndag 6 mars 2017 kl. 17:43:36 UTC+1 skrev gmhwxi:
>
> Yes, CSVstate needs to be changed as well.
>
> However, your code needs very little change. This is like a
> a 5 minute job to me. I would be happy to give it a try if you say so.
> But I thought that you might want to get the thrill of fixing the code :)
>
> On Monday, March 6, 2017 at 11:30:27 AM UTC-5, August Alm wrote:
>
> Hrrm, I had:
>
> fun
> parse_entry
> ( st: !CSVState >> _
> , at: (int, int)
> , acc: !$SBF.stringbuf
> , cs: llstring
> ) : stream_vt(CSVEntry)
>
> I gather I have to change not just [!$SBF.stringbuf] but also [!CSVState
> >> _], right? What about if I did
>
> fun
> parse_entry_con
> ( st: !CSVState >> _
> , at: (int, int)
> , acc: !$SBF.stringbuf
> , cs: llstring
> ) : stream_vt_con(CSVEntry)
>
> and then put
>
> parse_entry(...) =
> $ldelay
> ( parse_entry_con(...)
> , ( free(st)
> ; free(acc)
> ; free(cs)
> )
> )
>
> --would that work? Would it be idiomatic and efficient?
>
> Thanks, again,
> August
>
> Den måndag 6 mars 2017 kl. 14:30:05 UTC+1 skrev gmhwxi:
>
> I forgot to tell you something essential in using stream_vt.
> The following interface for 'test' cannot work:
>
> fun test (acc: !$SBF.stringbuf, cs: llstring): stream_vt(DT) =
>
> What you need is
>
> fun test (acc: $SBF.stringbuf, cs: llstring): stream_vt(DT) =
>
> The 'acc' stringbuf needs to be consumed by 'test'. The implementation
> of 'test' looks like this:
>
> $ldelay
> (
> <code for stream construction>
> ,
> (freeing(acc); freeing(cs)) // this part is executed when the stream is
> freed
> )
>
> On Mon, Mar 6, 2017 at 8:19 AM, August Alm <augu...@gmail.com> wrote:
>
> The points you mention are part of the reason I chose to wrote the csv
> lexer the way I did. It follows one of the fastests Haskell csv parsers,
> and I was curious to see how using linear types could optimize performance.
>
> Regarding your suggestion on how to make better use of $ldelay in my code:
> I'm stuck on a compiler error that I can't make sense of. The following
> pseudo-minimal example throws the same kind of errors:
>
> #include "share/atspre_define.hats"
> #include "share/atspre_staload.hats"
> staload UN = "prelude/SATS/unsafe.sats"
> staload SBF = "libats/SATS/stringbuf.sats"
> staload _(*SBF*) = "libats/DATS/stringbuf.dats"
>
> datatype DT = D_T of @{ alpha = char }
> vtypedef llstring = stream_vt(char)
>
> fun
> test (acc: !$SBF.stringbuf, cs: llstring): stream_vt(DT) =
> $ldelay
> ( case !cs of
> | ~stream_vt_nil() =>
> if $SBF.stringbuf_get_size(acc) = i2sz(0) then stream_vt_nil()
> else stream_vt_cons(D_T(@{alpha = 'a'}), stream_vt_make_nil())
> | ~stream_vt_cons(c, cs1) =>
> let val crec = D_T(@{alpha = c})
> in stream_vt_cons(crec, test(acc, cs1))
> end
> , ~cs
> )
>
> The compiler can not infer the type I want (which is [stream_vt_con(DT)]
> for the [stream_vt_nil()] following the first [then] in the function body.
> The error message says
>
> the dynamic expression cannot be assigned the type [S2EVar(5492)].
> [...] mismatch of sorts in unification:
> The sort of variable is: S2RTbas(S2RTBASimp(1; t@ype))
> The sort of solution is: S2RTbas(S2RTBASimp(2; viewtype))
> [...] mismatch of static terms (tyleq):
> The actual term is: S2Eapp(S2Ecst(stream_vt_con); S2EVar(5495))
> The needed term is: S2EVar(5492)
>
> (There are further errors of the same form.) Is the culprit that
> [stream_vt] of a nonlinear datatype requires some special care? The version
> with [stream_vt_make_nil()] instead of explicit [$ldelay] works so the
> error ought to be subtle.
>
> Best wishes,
> August
>
> Den söndag 5 mars 2017 kl. 23:58:35 UTC+1 skrev gmhwxi:
>
> Yes, you definitely got it :)
>
> Stream_vt is very memory-frugal.
>
> Haskell relies on deforestation (complex complier optimization)
> to reduce memory usage of lazy evaluation. In ATS, deforestation is
> not supported. Instead, the programmer needs to recycle memory explicitly.
>
> Compared to Haskell, corresponding code using stream_vt in ATS can be
> much more efficient both time-wise and memory-wise.
>
> For instance, the following example (for computing Mersenne primes) can
> run for days without run-time GC:
>
>
> https://github.com/githwxi/ATS-Postiats/blob/master/doc/EXAMPLE/RosettaCode/Lucas-Lehmer_test2.dats
>
> It convincingly attests to the power of linear streams.
>
> Cheers!
>
>
> On Sun, Mar 5, 2017 at 5:34 PM, August Alm <augu...@gmail.com> wrote:
>
> Thanks for the tip! I think I understand. I treated $ldelay much as a data
> constructor, so that all streams are equally lazy, whereas there are in
> fact many ways to sequence into thunks. Let me give an example to anchor
> the discussion. Both the following implementations of a map-template for
> linear streams typecheck:
>
> fun {a, b: t0ype}
> map_make_cons
> ( xs: stream_vt(a)
> , f: a -> b
> ) : stream_vt(b) =
> case !xs of
> | ~stream_vt_nil() => stream_vt_make_nil()
> | ~stream_vt_cons(x, xs1) =>
> stream_vt_make_cons(f(x), map_make_cons(xs1, f))
>
> fun {a, b: t0ype}
> map_ldelay
> ( xs: stream_vt(a)
> , f: a -> b
> ) : stream_vt(b) =
> $ldelay
> ( case !xs of
> | ~stream_vt_nil() => stream_vt_nil()
> | ~stream_vt_cons(x, xs1) =>
> stream_vt_cons(f(x), map_ldelay(xs1, f))
> , ~xs
> )
>
> The second is maximally lazy. The first, [map_make_cons] is less lazy
> because checking the case-conditions is not delayed. My code was like the
> first example, only much more was going on inside the case expressions. Is
> that a correct assessment?
>
>
> Den söndag 5 mars 2017 kl. 04:07:42 UTC+1 skrev gmhwxi:
>
> BTW, it seems you don't need to do much to fix the issue.
>
> Basically, you just do
>
> 1) Put the body of parse_entry into $ldelay(...)
> 2) Change stream_vt_make_cons into stream_vt_cons
>
> There may be a few other things but they should all be
> very minor.
>
> On Saturday, March 4, 2017 at 9:47:07 PM UTC-5, gmhwxi wrote:
>
> I took a glance at your code.
>
> I noticed a very common mistake involving the use of
> stream (or stream_vt). Basically, the way stream is used
> in your code is like the way list is used. This causes the
> stack issue you encountered.
>
> Say that you have a function that returns a stream. In nearly
> all cases, the correct way to implement such a function should
> use the following style:
>
> fun foo(...): stream_vt(...) = $ldelay
> (
> ...
> )
>
> The idea is that 'foo' should return in O(1) time. The body of $ldelay
> is only evaluated with the first element of the returned stream is neede.
> Sometimes, this is call full laziness. Without full laziness, a stream may
> behave like a list, defeating the very purpose of using a stream.
>
> On Saturday, March 4, 2017 at 7:27:03 PM UTC-5, August Alm wrote:
>
> I've spent few hours trying to figure out how to make proper use of npm
> and gave up--for now. If the project turns into something more serious
> (i.e., useful to others) then I will have another go at it. For now my
> naive attempts at making effective use of linear streams can be witnessed
> at GitHub: https://github.com/August-Alm/ats_csv_lexer Any and all
> comments on how to improve are appreciated.
>
> Best wishes, August.
>
> Den fredag 3 mars 2017 kl. 23:57:54 UTC+1 skrev gmhwxi:
>
> One possibility is to build a npm package and then publish it.
>
> If you go to https://www.npmjs.com/ and seach for 'atscntrb'. You can find
> plenty packages. You may need to install npm first.
>
> If you do build a npm package, I suggest that you choose a name space for
> yourself. E.g., atscntrb-a?a-..., where ? is the first letter of your
> middle name.
>
> On Fri, Mar 3, 2017 at 5:48 PM, August Alm <augu...@gmail.com> wrote:
>
> How would I best share larger code portions? I have no concerns about my
> making my mistakes public, heh.
>
> I believe everything is lazy as-is (all data is [stream_vt("sometype")]).
> And I've tried to write tail-recursive functional code. The algorithm is
> based on two mutually recursing functions, "fun ... and ..", similar to how
> you did things in your csv-parser (thanks for pointing out that piece of
> code). However, I cannot set them up with "fn* .. and .." to enforce a
> local jump because they call each other in a too intertwined way. Might
> that be it?
>
>
> Den fredag 3 mars 2017 kl. 23:32:15 UTC+1 skrev gmhwxi:
>
> You are welcome!
>
> Since I have not seen your code, I could only guess :)
>
> Usually, what you described can be fixed by using tail-recursion, or
> by using lazy-evaluation. The former approach is straightforward. You
> just need to identify the function or functions that cause the deep stack
> usage. Then try to rewrite using tail-recursion.
>
>
>
> On Fri, Mar 3, 2017 at 5:25 PM, August Alm <augu...@gmail.com> wrote:
>
> Hi!
> I had indeed made a logical error that caused any stream with "carriage
> return" followed by "newline" to recurse indefinitely. Thank you for your
> patience and pedagogical instincts, Professor! There is still some issue
> though, one that I believe is more subtle. I fixed the logical error and my
> algorithm now handles all the test cases you suggested. However, when fed
> an actual CSV-file with a thousand rows and about 300 columns it still
> segfaults--unless I manually increase the stack space on my computer! I
> don't know exactly where the critical limit is, but increasing it from 8192
> kbytes to 65536 certainly did the trick. The whole file parsed without
> problem, and rather quickly at that. It seems my algorithm makes too much
> use of stack allocation and that I may have to rethink some of my
> (would-be) optimization choices.
> Best wishes,
> August
>
> Den fredag 3 mars 2017 kl. 15:22:00 UTC+1 skrev gmhwxi:
>
> Now you may do the following tests:
>
> Try:
>
> val ins = streamize_string_char("a;b") // should work
>
> Try:
>
> val ins = streamize_string_char("a;b\n") // may not work
>
> Try:
>
> val ins = streamize_string_char("a;b\015\012") // should cause crash
>
> On Thursday, March 2, 2017 at 9:21:21 PM UTC-5, gmhwxi wrote:
>
> When tried, I saw the following 5 chars (ascii) in small.csv:
>
> 97
> 59
> 98
> 13
> 10
>
> My testing code:
>
> #include"share/atspre_staload.hats"
> #include"share/HATS/atspre_staload_libats_ML.hats"
>
> implement main0 () = {
> val inp = fileref_open_exn("small.csv", file_mode_r)
> val ins = streamize_fileref_char(inp)
> val ins = stream2list_vt(ins)
> val ins = g0ofg1(list_vt2t(ins))97
> val ( ) = println! ("length(ins) = ", length(ins))
> val ( ) = (ins).foreach()(lam c => println!(char2int0(c)))
> (*
> val lexed = lex_csv(true, ';', ins)
> *)
> val () = fileref_close(inp)
> (*
> val h = (lexed.head())
> val- CSV_Field(r) = h
> val a = r.csvFieldContent
> val () = println!(a)
> *)
> }
>
>
>
> On Thu, Mar 2, 2017 at 9:13 PM, August Alm <...> wrote:
>
> Just "a;b", or? (Attached.)
>
> Den fredag 3 mars 2017 kl. 03:03:08 UTC+1 skrev gmhwxi:
>
> I suspect that the file you used contains other characters.
>
> What is in "small.csv"?
>
> On Thu, Mar 2, 2017 at 8:52 PM, August Alm <...> wrote:
>
> The file compiles (I've tried a few compiler options) and "gdb run" yields
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00007ffff783eea5 in _int_malloc (av=0x7ffff7b6a620 <main_arena>,
> bytes=16) at malloc.c:3790
>
> The frames 0-3 involve allocation functions that are not particular to my
> file. Frame 4 says:
>
> #4 __patsfun_28__28__14 (arg0=<optimized out>, env1=0x605540, env0=10
> '\n') at csv_lexer_dats.c:9023
> 9023 ATSINSmove_con1_new(tmpret63__14, postiats_tysum_7) ;
>
> My not-so-educated guess is that this refers to making a cons-cell of a
> stream.
>
> But: How can my function do just fine when manually fed
>
> cons('a', cons( ';', sing('b'))): stream_vt(char),
>
> but segfault when I use [streamize_fileref_char] to construct the very
> same stream from the string "a;b" in a file? Where is the room for an
> infinite recursion in that?
>
> Thank you,
> August
>
>
> Den torsdag 2 mars 2017 kl. 23:04:35 UTC+1 skrev August Alm:
>
> Hi!
>
> I'm in over my head and tried writing a CSV-parser using linear lazy
> streams. My code thus far is 600 lines and almost to my own surprise I get
> it to compile! However, there is something fishy because I get a segfault
> when applying my program to an actual CSV-file. I've been trying to debug
> using gdb but the fault eludes me. Since I don't expect anyone to mull
> through 600 lines of code, I am hoping these code snippets are enough for
> one of you guys to give me some advice.
>
> This code executes just fine:
>
> implement main0 () = {
>
> val test = stream_vt_make_cons(
> 'a', stream_vt_make_cons(
> ';',
> stream_vt_make_sing('b'))) (* the stream ('a', ';', 'b') *)
> val lexed = lex_csv(true, ';', test)
> val h = (lexed.head())
> val- CSV_Field(r) = h
> val a = r.csvFieldContent
> val () = println!(a)
>
> }
>
> Here [lex_csv] is my 600-line alogrithm. It reads a [stream_vt(char)] and
> gives back a [stream_vt(CSVEntry)], where [CSVEntry] is a record type, one
> of whose fields is [CSVFieldContent]. When executing the program I get "a"
> printed to the console.
>
> This code results in a segfault:
>
> implement main0 () = {
>
> val inp = fileref_open_exn("small.csv", file_mode_r)
> val ins = streamize_fileref_char(inp)
> val lexed = lex_csv(true, ';', ins)
> val () = fileref_close(inp)
> val h = (lexed.head())
> val- CSV_Field(r) = h
> val a = r.csvFieldContent
> val () = println!(a)
>
> }
>
> The file "small.csv" only contains the string "a;b". Hence I would expect
> this code to give the result as the previous one! But, it doesn't just
> return something else, it segfaults.
>
> gdb indicates there is a malloc problem having to do with
> "GC_clear_stack_inner", in case that's helpful. (I'm a mathematician who
> recently left academia after postdoc and decided to teach myself
> programming to become more useful outside of academia; hence I understand
> type systems and the like--the mathy stuff--a lot better than I understand
> memory allocation and other stuff that most programmers are supposed to be
> confident with.)
>
> What could be the problem here?
>
> Best wishes,
> August
>
> ...
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