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 <[email protected]> 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 [email protected]. > > 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
