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Loading C-coded Functions into CL or Maxima

The mechanism outlined in the previous section is recommended for including codes writing in another language into maxima (AKCL). However, there is also a mechanism similar to the Franz cfasl available in maxima (AKCL).

Basically, this involves a compiled C file cfile.o (by cc) and a lisp wrapper file lispfile.o (by lc or mc). The wrapper defines lisp functions that interface to the C-coded functions. These two files are loaded into akcl or maxima with the lisp function si::faslink.

Here is an example of defining a function similar to fopen for akcl. The C file is process.c and the lisp file is proc.lsp.

/********************* file process.c  *******************************/
#include <stdio.h>

static FILE *pstm;

process(cmd, mode)        /* run process ,  mode must be "w" */
char *cmd;
char *mode;
{     pstm = popen(cmd, mode);
      if ( pstm == NULL) return(1);
      return(0);
}

prwrite(str)               /* write to stdin of process */
char *str;
{     fprintf(pstm, "%s\n", str);
      fflush(pstm);
      return(0);
}

prclose()                  /* close stream to process */
{     fclose(pstm);
      return(0);
}

(in-package 'system)

;;  defines lisp function process to access C function process 
;;  by passing two lisp string args to the C function and
;;  receives an integer return value
(defentry process (string string) (int process))

;;  these are similar
(defentry prwrite (string) (int prwrite))
(defentry prclose () (int prclose))

(si:faslink "proc.o" "process.o -lc")

The AKCL/BSD specific si:faslink is given in the form

(si:faslink file string)