On Thursday, June 29, 2017 at 11:22:38 AM UTC-4, David K. Storrs wrote: > On Thu, Jun 29, 2017 at 11:10 AM, Sam Waxman <samw...@gmail.com> wrote: > Hey all, > > > > I'm writing a #lang and am trying to raise my own errors instead of having > racket throw any errors of its own. > > > > One of my constructs, (func name(args) body), defines a function that's able > to be called afterwards, and it desugars into a pretty regular define > statement. As a result, I can't do things like > > > > (let () (func a(x) x)) > > (+ (func a(x) x) 1) > > etc ... > > > > because it ends up expanding into a define statement in an expression > position, which is bad. > > > > While I don't want this to be allowed, I'd like to catch this and throw my > own errors if this happens. The only way I can really imagine doing this is > to modify all the functions I have that take in expressions (+ - * / let ...) > > and give them contracts that say "Hey, check to make sure your arguments are > expressions, and if not, throw this syntax error!" > > > > The only problem there is that I can't seem to find any function that will > tell me if I have an expression or a define. Is there an easy way to check > this? I.e. a function expression? such that > > > > (expression? #'(+ 1 1)); #t > > (expression? #'(define a 1)); #f > > (expression? #'(define-syntax-rule (id x) x)); #f > > > > > > It'd be nice if there was a function like this, but also, if there's an > easier way to do this, by all means, lemme know! > > > > Thanks in advance. > > > > > > I think you want 'splicing-let': > > #lang racket > > (require racket/splicing) > > (splicing-let () > (define (foo a) a) > (foo 'x)) > (foo 'y) > > > Ouput: > > > 'x > > 'y > > I'm not actually trying to get the define statements to define things here, > or to splice them into the surrounding environment, I'm just trying to throw > my own custom error messages/define my own custom behavior when you put > defines in expression positions. So
(my+ 1 (func a(x) x)) shouldn't work, but instead of racket's error messages, I'd like to throw one like "The arguments to + must be expressions. Recieved a function definition for argument 2." I'd also be interested in changing (my-let () (func a(x) x)) to expand into (my-let () (func a(x) x) (values)) so racket doesn't throw an error when func's are the final bodies in a let statement. But the issue isn't that I want to splice these defines, it's that I need a way of checking in my+, my-let, my-, my/ ... (which are all macros I've written for my languages' +, let, -, / ...) to see if the arguments they have are expressions or define statements. > -- > > 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...@googlegroups.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. For more options, visit https://groups.google.com/d/optout.
