>>>>> "GP" == GP lisper <[EMAIL PROTECTED]> writes:
>>> Is there a better callback example someplace? One that has
>>> c-subroutines calling lisp?
>>
>> <http://www.cons.org/cmucl/doc/tcl-callback.html>
>>
>> Cheers,
>> Edi.
[snip]
GP> Can those header files be mentioned on the cited callback webpage?
Yes, we can do that, but CMUCL now has callbacks integrated better
(thanks to work by Helmut Eller). I guess the html version of the
manual is out of date, but the TeX sources contains information about
the new callback mechanism.
I've appended the relevant section from the manual that describes
this. If this doesn't do what you need it to do, please let us know.
Ray
\cmucl{} supports calling Lisp from C via the \funref{def-callback}
macro:
\begin{defmac}{alien:}{def-callback}{\var{name} (\var{return-type}
\mstar{(arg-name arg-type)})}
This macro defines a Lisp function that can be called from C and a
Lisp variable. The arguments to the function must be alien types,
and the return type must also be an alien type. This Lisp function
can be accessed via the \funref{callback} macro.
\var{name} is the name of the Lisp function. It is also the name of
a variable to be used by the \code{callback} macro.
\var{return-type} is the return type of the function. This must be
a recognized alien type.
\var{arg-name} specifies the name of the argument to the function,
and the argument has type \var{arg-type}, which must be an alien type.
\end{defmac}
\begin{defmac}{alien:}{callback}{\var{callback-symbol}}
This macro extracts the appropriate information for the function
named \var{callback-symbol} so that it can be called by a C
function. \var{callback-symbol} must be a symbol created by the
\code{def-callback} macro.
\end{defmac}
\begin{defmac}{alien:}{callback-funcall}{\var{callback-name} \amprest
\var{args}}
This macro does the necessary stuff to call the callback named
\var{callback-name} with the given arguments.
\end{defmac}
\subsection{Callback Example}
Here is a simple example of using callbacks.
\begin{lisp}
(use-package :alien)
(use-package :c-call)
(def-callback foo (int (arg1 int) (arg2 int))
(format t "~&foo: ~S, ~S~%" arg1 arg2)
(+ arg1 arg2))
(defun test-foo ()
(alien-funcall (sap-alien (callback foo) (function int int int))
555 444444))
\end{lisp}
In this example, the callback function \code{foo} is defined which
takes two C \code{int} parameters and returns a \code{int}. As this
shows, we can use arbitrary Lisp inside the function.
The function \code{test-foo} shows how we can call this callback
function from Lisp. The macro \code{callback} extracts the necessary
information for the callback function \code{foo} which can be
converted into a pointer which we can call via \code{alien-funcall}.
The following code is a more complete example where a foreign routine
calls our Lisp routine.
\begin{lisp}
(use-package :alien)
(use-package :c-call)
(def-alien-routine qsort void
(base (* t))
(nmemb int)
(size int)
(compar (* (function int (* t) (* t)))))
(def-callback my< (int (arg1 (* double))
(arg2 (* double)))
(let ((a1 (deref arg1))
(a2 (deref arg2)))
(cond ((= a1 a2) 0)
((< a1 a2) -1)
(t +1))))
(defun test-qsort ()
(let ((a (make-array 10 :element-type 'double-float
:initial-contents '(0.1d0 0.5d0 0.2d0 1.2d0 1.5d0
2.5d0 0.0d0 0.1d0 0.2d0 0.3d0))))
(print a)
(qsort (sys:vector-sap a)
(length a)
(alien-size double :bytes)
(alien:callback my<))
(print a)))
\end{lisp}
We define the alien routine, \code{qsort}, and a callback, \code{my<},
to determine whether two \code{double}'s are less than, greater than
or equal to each other.
The test function \code{test-qsort} shows how we can call the alien
sort routine with our Lisp comparison routine to produce a sorted
array.
