Re: [Chicken-users] pass by value and callbacks

[r]

Hello pluijzer

As i know chicken didnt have pass-by-value FFI type.
This is little bit verbose workaround. Note that you should use 
foreign-safe-lambda for callbacks from C.



(import scheme chicken foreign)

#
typedef struct { int x, y; } Point;

typedef void (*SomeCallbackFuncType)(Point point);

void someFunc(SomeCallbackFuncType callback)
{
Point p = {1, 1};
callback(p);
}

static void callbackFunctionJumper(Point point)
{
   callbackFunction(point);
}
#

(define-external (callbackFunction (c-pointer point))
  void
  (print Hello from callback!))

((foreign-safe-lambda* void () someFunc(callbackFunctionJumper);))



Hello chickeners,

I am trying to wrap a function that accepts a function pointer with an
argument to a struct passed by value.
I don't know how to do this (and fear it is not possible) but maybe
somebody else has a solution.

A little example of what I mean:



#
typedef struct { int x, y; } Point;

typedef void (*SomeCallbackFuncType)(Point point);

void someFunc(SomeCallbackFuncType callback)
{
 Point p = {1, 1};
 callback(p);
}
#

(define-external (callbackFunction (??? point))
   void
   (print Hello from callback!))

((foreign-lambda void someFunc c-pointer) #$callbackFunction)



I don't actually need the the value of the object in my callback.
Maybe that helps.

Thank you in advance,
Pluijzer

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Re: [Chicken-users] Review my Caesar Cipher?

[Alex Shinn]

On Tue, Mar 11, 2014 at 9:20 PM, Daniel Carrera dcarr...@gmail.com wrote:


 On 11 March 2014 12:41, Alex Shinn alexsh...@gmail.com wrote:

 Chibi has string-map in (chibi string).

 But actually, if you're aiming for R7RS support then
 string-map is in (scheme base).  Just replace the
 cond-expand with:

 (import (scheme base))


 Hmm... sadly, (import (scheme base)) fails with Chicken and Gauche. I am
 also having a hard time figuring out how to print with Chibi. I tried the
 manual, and I tried (print), (printf) and (display).


Then change your cond-expand to:

(cond-expand
 ((or chicken gauche)  ; compatibility
  (use srfi-13))
 (else ; R7RS
  (import (scheme base) (scheme write

R7RS puts display in (scheme write), because it typically
falls back to write for non-char/strings, and because write
is actually a fairly large and complicated procedure not
needed by most libraries.

However, write-char, write-string and newline are all in
(scheme base) so you could just use write-string here.

You can also (import (scheme r5rs)) to get all of the R5RS
bindings except transcript-on/off.

-- 
Alex
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