Just came here to say: Congratulations Linus! That was definitely the most important part of your message :-).
Aleix On Tue, Aug 30, 2022 at 3:48 AM Linus Björnstam < linus.bjorns...@veryfast.biz> wrote: > I am working on a patch to guile to add definitions to just about every > body except for (begin ...) outside definition context. > > The patch is trivial, but I have to document it and a patch to r6rs that > makes the r6rs cons work according to spec. > > I had a kid recently so it might take some time before I have any computer > time, so if anyone has some time this is a really simple thing. You can > find the first patch somewhere in this mailing list, it only changes the > (begin ...)s in the derived forms in (ice-9 boot-9) to (let () ...). Then i > was going to copy the cond and case from the r6rs appendix and add some > error reporting. > > The most difficult part is documenting it :) > > Andy have the idea hos blessing, and will mean guile gets define in > expression context in when, unless, cond, case, while, and do as well as in > derived forms. > > -- > Linus Björnstam > > On Sat, 27 Aug 2022, at 18:48, Damien Mattei wrote: > > Hello, > > > > i'm facing sometimes recursively the problem to have definitions in > > expression context, which i manage every time by adding an upper empty > > (let () my definitions goes here ) > > the last case i was facing this probleme is defining a 'for macro: > > > > ;; scheme@(guile-user)> (for ({i <+ 0} {i < 5} {i <- {i + 1}}) (display > > i) (newline)) > > ;; 0 > > ;; 1 > > ;; 2 > > ;; 3 > > ;; 4 > > > > > > (define-syntax for > > > > (syntax-rules () > > > > ((_ (init test incrmt) b1 ...) > > > > (let () > > init > > (let loop () > > (when test > > b1 ... > > incrmt > > (loop))))))) > > > > this one fails in my Scheme+ code below: > > (define (compute-carries n) > > > > (for ( {k <+ 0} {k <= n} {k <- {k + 1}} ) > > > > { Ckp1 <+ (compute-Ck-plus1 k) } > > (display-nl Ckp1))) > > > > because { Ckp1 <+ (compute-Ck-plus1 k) } expands in : > > (define Ckp1 (compute-Ck-plus1 k)) > > and i get a compilation error: > > ;;; Syntax error: > > ;;; logic-syracuse+.scm:15:7: definition in expression context, where > > definitions are not allowed, in form (define Ckp1 (compute-Ck-plus1 k)) > > > > so i replace my 'for macro definition with: > > > > (define-syntax for > > > > (syntax-rules () > > > > ((_ (init test incrmt) b1 ...) > > > > (let () > > init > > (let loop () > > (when test > > (let () > > b1 ... > > incrmt > > (loop)))))))) > > > > and it works, but you will notice an abusive use of empty (let () ...) > > in the code to avoid the restrictions of definitions not allowed in > > expression context. > > > > My ideas is as it is so easy to cheat the compiler from seeing the > > expressio context why does the compiler restrict this? expression and > > defintion context, i'm not sure they are in scheme standarts, are they > > really usefull? > > why not remove this from Scheme at all? > > > > Regards, > > > > Damien > >