Marc,

Thank you for your reply.  This was exactly what I was looking for.  Is the "Gambit_js2scm" function available in v4.7.2, or will I need to upgrade to the latest code?

I'm glad to hear you are continuing to improve the universal backend and am excited that first-class continuations are now implemented.  With first-class continuations available are there plans to implement green threads as well?  I've thought that green threads may be a interesting method to implement sprites for a HTML5 game.

Bob

On Thursday, March 6, 2014 2:23 AM, Marc Feeley feeley@iro.umontreal.ca wrote:

On Mar 5, 2014, at 5:19 PM, Bob Coleman bobcolem@yahoo.com wrote:

Greetings,

I have been playing around with the javascript backend and have been impressed with it's capabilities.

I’m glad you like it.  Over the past week I have made several enhancements with the short term goal of implementing a remote debugger (so that Scheme code running in the browser can be debugged live using a REPL running on the server).  Just a few minutes ago I committed the support for first-class continuations which are needed for the exception handling of the REPL.

Interacting with other javascript libraries is not a problem, but I haven't found a way for other javascript code to call scheme defined functions.  Is there a way to define functions to be called by javascript similar to c-lambda or c-define?

It is quite easy to interface to JavaScript functions from Scheme.  In fact, using JavaScript’s eval gives a much simpler approach than using Gambit’s C interface for the C back-end.  For example, you can define

(define js   (##inline-host-expression "Gambit_js2scm(eval)"))

This creates a Scheme callable function which performs a JavaScript eval.  Then, in your code you can say:

(define alert (js "alert")) (alert "hello!")

This will “convert” the JavaScript “alert” function to a Scheme function.

For the other way around (exporting a Scheme function callable from JavaScript), the js function can be used like this:

(define setglo (js "function (name,val) { window[name] = val; }"))

then

(setglo "foo" (lambda (n) (* n n)))

And then in JavaScript land your can call (foo 10).

Also, is it possible to access the value of the -target flag in scheme?  I would like to define some functions differently based on whether the program is being built for the C or javascript backend.

Define this macro:

(##define-macro (case-target . clauses)   (let ((target (if (and (pair? ##compilation-options)                           (pair? (car ##compilation-options)))                     (let ((t (assq 'target ##compilation-options)))                       (if t (cadr t) 'c))                     'c)))     (let loop ((clauses clauses))       (if (pair? clauses)           (let* ((clause (car clauses))                   (cases (car clause)))             (if (or (eq? cases 'else)                     (memq target cases))                 `(begin ,@(cdr clause))                 (loop (cdr clauses))))           `(begin)))))

and use it like this:

(case-target

((c)     (define foo (c-lambda () int "foo")))   ((js)     (define foo (lambda () (##inline-host-expression "42")))))

Marc

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On Mar 6, 2014, at 2:22 AM, Marc Feeley feeley@iro.umontreal.ca wrote:

For the other way around (exporting a Scheme function callable from JavaScript), the js function can be used like this:

(define setglo (js "function (name,val) { window[name] = val; }"))

then

(setglo "foo" (lambda (n) (* n n)))

And then in JavaScript land your can call (foo 10).

Ha! I meant foo(10) of course!

Marc

On May 16, 2014, at 9:29 AM, Mikael mikael.rcv@gmail.com wrote:

Dear Marc,

Did ##inline-host-expression (and ##inline-host-statement) change name recently?

On 4.7.2 it compiles to an ordinary procedure call.

Test case: (define js (##inline-host-expression "myprocedure(myargument)")) compiles to: .... return Gambit_glo['##inline-host-expression']();

This is even while grep -r inline-host-expression gambit/* gives:

./gambit/gsc/_t-univ.scm:(univ-prim-proc-add! '("##inline-host-expression" (1) #t 0 0 (#f) extended)) ./gambit/gsc/_t-univ.scm:(univ-define-prim "##inline-host-expression" #f ./gambit/gsc/_t-univ.scm: (compiler-internal-error "##inline-host-expression requires a constant string argument"))))

so it seems to be there somehow.

Thanks and best regards, Mikael

You need to

(declare (extended-bindings) (not safe))

for those procedures to be inlined.

I may change the “safety” of those procedures though because others have had similar problems.

Also I will add tests to avoid JS-level errors when calling an undefined global variable.

Marc