Yes -- you can always meta-program as much as you want, although: * meta-programming support is limited for string functions -- I think only String.length can be meta-evaluated * the chapter on meta-programming Low* hasn't been written yet in the tutorial đ.
~ jonathan ________________________________ From: fstar-club <fstar-club-boun...@lists.gforge.inria.fr> on behalf of Clément Pit-Claudel via fstar-club <fstar-club@lists.gforge.inria.fr> Sent: Wednesday, May 2, 2018 8:44 AM To: fstar-club@lists.gforge.inria.fr Subject: Re: [fstar-club] Trying to use List.Tot.map with Kremlin I'd expect the following to work, though. Does it? let main () = C.print_string (C.string_of_literal (normalize_term (String.concat ", " ["hello"; "world"]))); C.exit_success ⊠though maybe we don't apply `normalize_term` early enough. Clément. On 2018-05-02 11:08, Jonathan Protzenko via fstar-club wrote: > Yes, this is something that has poor usability. Prims.string and > FStar.String.concat are supported as transition mechanisms to help porting F* > programs to Low* but I agree that it's confusing for beginners to have them > work "by default". > > https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ffstarlang.github.io%2Flowstar%2Fhtml%2FLowStar.html%23c-string-literals&data=02%7C01%7Cprotz%40microsoft.com%7C6270df4eb0a244eaac3908d5b043b2d5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636608727210614165&sdata=ffbZwtJJ2ud7JXMhD56SL3Kyv15X%2BEYQT87%2Bc%2BlLFgY%3D&reserved=0 > has a note that explains it, my plan is to make it a warning that's fatal by > default, and that can be disabled if you need these mechanisms > > ~ jonathan > > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > *From:* Pierre Beaucamp <m...@pierrebeaucamp.com> > *Sent:* Tuesday, May 1, 2018 4:38 PM > *To:* Jonathan Protzenko; Pierre Beaucamp via fstar-club > *Subject:* Re: [fstar-club] Trying to use List.Tot.map with Kremlin > > Thanks for the quick answer Jonathan. > > I already assumed that this is caused by limited inter-polarity between F* > strings and their representation in Low*. What threw me off is that this code > works: > > let main () = > C.print_string (C.string_of_literal (String.concat ", " ["hello"; > "world"])); > C.exit_success > > Either way, I'm excited for the Low* tutorial - thank you for writing it. > This is a very interesting language with unfortunately very little > documentation for new-comers (I'm pretty much trying to learn F* and Low* at > the same time, and I guess this is where a lot of the confusion is coming > from). > > Thank you and best regards, > > -- > Pierre Beaucamp > > On Tue, May 1, 2018, at 7:09 PM, Jonathan Protzenko wrote: >> Hello Pierre, >> >> These are all excellent questions -- I am currently writing a tutorial >> for Low* are these served as good inspiration for the introduction. If >> CI goes through, a work-in-progress version of the tutorial should be >> uploaded in the next few hours at >> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ffstarlang.github.io%2Flowstar%2F&data=02%7C01%7Cprotz%40microsoft.com%7Cdb40113318a44ce8c0be08d5afbc9c55%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636608146970557404&sdata=aLvfTn4cd9Wrvck8prnVvnQfEA9I3BPpp1%2BE0PkjGpw%3D&reserved=0 >> -- please read it and let me know whether after browsing it, your >> questions have been answered. >> >> In case the CI doesn't perform the upload, or the tutorial is unclear, >> the essence of your issue is that your code is not Low*. >> >> * the F* string and list types are F* values, i.e. concat has type >> string -> string -> string; the only way to give you these semantics >> without requiring the user to track allocations and lifetimes is to use >> a garbage-collector, which C does not have >> * the same goes for lists: compiling them to C with the current F* >> value semantics would lead to a zillion uncollected list cell >> allocations. >> >> What the C.String module provides is a bare-bones model of C string >> literals, i.e. `const char *s = "my string literal";`, meaning that you >> should provide an actual literal, e.g. `C.String.( print !$"hello, world >> \n" );`. This is very limited, and does not allow you to do arbitrary >> string manipulation. >> >> A proof-of-concept example exists that does that, in the test/ >> subdirectory of KreMLin, and is called Server.fst. It models blitting >> C.String.t's into a mutable buffer of C chars, tracking how much space >> remains in your buffer, whether the buffer is live, etc. and rules out >> buffer overflows. >> >> Naturally, it's a little involved for a hello world, but I guess that's >> the reality of tracking temporal (liveness) and spatial safety (bounds) >> in C. >> >> Let me know if that helps. >> >> Cheers, >> >> Jonathan >> >> >> ~ jonathan >> >> ________________________________ >> From: fstar-club <fstar-club-boun...@lists.gforge.inria.fr> on behalf of >> Pierre Beaucamp via fstar-club <fstar-club@lists.gforge.inria.fr> >> Sent: Tuesday, May 1, 2018 9:48 AM >> To: fstar-club@lists.gforge.inria.fr >> Subject: [fstar-club] Trying to use List.Tot.map with Kremlin >> >> Hi everyone, >> >> I'm just playing a bit around with F-Star and Kremlin and I seem to be >> stuck at a simple problem. I don't know if I'm missing something obvious >> or if this might be a bug. My code looks like this: >> >> let main () = >> C.print_string (C.string_of_literal (String.concat ", >> " (List.Tot.map string_of_int [1; 2; 3]))); >> C.exit_success >> >> I expect this code to print `1, 2, 3` but instead I get the following >> runtime error: >> >> KreMLin abort at ./Main.c:9 >> This function was not extracted: >> Failure("Cannot extract string_of_literal applied to a non-literal") >> >> I tried some variations of the above program to see if I can reverse- >> engineer what is going on, but as soon as I introduce `List.Tot.map`, >> the code breaks. I know that there is also `C.Loops.map`, but I don't >> know if I really need to use buffers to make it work. >> >> Also, I'm generally interested in learning more about Kremlin / Low* / >> F*. If there are any recommended resources or other helpful links, feel >> free to share them with me. >> >> Thank you and best regards, >> >> -- >> Pierre Beaucamp >> _______________________________________________ >> fstar-club mailing list >> fstar-club@lists.gforge.inria.fr >> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.gforge.inria.fr%2Fmailman%2Flistinfo%2Ffstar-club&data=02%7C01%7Cprotz%40microsoft.com%7C445acbbb8a104079b70808d5af83d2b8%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636607903120375441&sdata=WkxhslLqaMBwupJazX4IDfRaWwsqX6IIiuWZT8YrwFc%3D&reserved=0 > > > _______________________________________________ > fstar-club mailing list > fstar-club@lists.gforge.inria.fr > https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.gforge.inria.fr%2Fmailman%2Flistinfo%2Ffstar-club&data=02%7C01%7Cprotz%40microsoft.com%7C6270df4eb0a244eaac3908d5b043b2d5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636608727210624175&sdata=NfYXtrOcH1uADk53hQ4SU%2B0ZbpfLtPWUqDZI97EgCyA%3D&reserved=0 > _______________________________________________ fstar-club mailing list fstar-club@lists.gforge.inria.fr https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.gforge.inria.fr%2Fmailman%2Flistinfo%2Ffstar-club&data=02%7C01%7Cprotz%40microsoft.com%7C6270df4eb0a244eaac3908d5b043b2d5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636608727210624175&sdata=NfYXtrOcH1uADk53hQ4SU%2B0ZbpfLtPWUqDZI97EgCyA%3D&reserved=0
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