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<!DOCTYPE html>
<html lang="en">
<!-- documentation for s7 -->
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" >
<title>s7-ffi</title>
<style>
EM.red {color:red; font-style:normal}
EM.normal {font-style:normal}
EM.redb {color:red; font-weight: bold; font-style: normal}
EM.error {color:chocolate; font-style:normal}
EM.emdef {font-weight: bold; font-style: normal}
EM.green {color:green; font-style:normal}
EM.gray {color:#505050; font-style:normal}
EM.big {font-size: 20px; font-style: normal;}
EM.bigger {font-size: 30px; font-style: normal;}
EM.def {font-style: normal}
H1 {text-align: center}
UL {list-style-type: none}
A {text-decoration:none}
A:hover {text-decoration:underline}
A.def {font-weight: bold;
font-style: normal;
text-decoration:none;
}
PRE.indented {padding-left: 1.0cm;}
DIV.indented {background-color: #F8F8F0;
padding-left: 0.5cm;
padding-right: 0.5cm;
padding-top: 0.5cm;
padding-bottom: 0.5cm;
margin-bottom: 0.5cm;
border: 1px solid gray;
border-radius: 20px;
-moz-border-radius: 20px;
-webkit-border-radius: 20px;
}
DIV.small {font-size: small;
padding-left: 0.5cm;
padding-right: 0.5cm;
padding-bottom: 0.5cm;
}
DIV.header {margin-top: 60px;
margin-bottom: 30px;
border: 4px solid #00ff00; /* green */
background-color: #eefdee; /* lightgreen */
padding-left: 30px;
}
DIV.shortheader {margin-top: 30px;
margin-bottom: 10px;
border: 4px solid #00ff00; /* green */
background-color: #f5f5dc;
padding-left: 30px;
padding-top: 5px;
padding-bottom: 5px;
width: 20%;
}
DIV.topheader {margin-top: 10px;
margin-bottom: 40px;
border: 4px solid #00ff00; /* green */
background-color: #f5f5dc; /* beige */
font-family: 'Helvetica';
font-size: 30px;
text-align: center;
padding-top: 10px;
padding-bottom: 10px;
}
DIV.separator {margin-top: 30px;
margin-bottom: 10px;
border: 2px solid #00ff00; /* green */
background-color: #f5f5dc; /* beige */
padding-top: 4px;
width: 30%;
border-radius: 4px;
-moz-border-radius: 4px;
-webkit-border-radius: 4px;
}
DIV.smallseparator {margin-top: 10px;
margin-bottom: 10px;
border: 2px solid #00ff00; /* green */
background-color: #f5f5dc; /* beige */
padding-top: 4px;
width: 20%;
border-radius: 4px;
-moz-border-radius: 4px;
-webkit-border-radius: 4px;
text-align: center;
}
BODY.body {background-color: #ffffff; /* white */
margin-right: 20px;
margin-left: 20px;
}
DIV.listener {background-color: #f0f8ff;
font-family: 'Monospace';
padding-left: 6px;
padding-right: 6px;
padding-bottom: 4px;
margin-left: 1.0cm;
margin-right: 4.0cm;
border: 2px solid #a0a0a0;
}
LI.li_header {padding-top: 20px;}
</style>
</head>
<body class="body">
<div class="topheader" id="FFIexamples">FFI examples</div>
<ul>
<li><a href="s7-ffi.html#repl">read-eval-print loop (and emacs)</a>
<li><a href="s7-ffi.html#defun">define a function with arguments and a returned value, and define a variable </a>
<li><a href="s7-ffi.html#defvar">call a Scheme function from C, and get/set Scheme variable values in C</a>
<li><a href="s7-ffi.html#juce">C++ and Juce</a>
<li><a href="s7-ffi.html#sndlib">load sndlib using the Xen functions and macros</a>
<li><a href="s7-ffi.html#pwstype">add a new Scheme type and a procedure with a setter</a>
<li><a href="s7-ffi.html#functionportexample">redirect display output to a C procedure</a>
<li><a href="s7-ffi.html#extendop">extend a built-in operator ("+" in this case)</a>
<li><a href="s7-ffi.html#definestar1">C-side define* (s7_define_function_star)</a>
<li><a href="s7-ffi.html#definemacro1">C-side define-macro (s7_define_macro)</a>
<li><a href="s7-ffi.html#definegeneric">define a generic function in C</a>
<li><a href="s7-ffi.html#signal">signal handling (C-C to break out of an infinite loop)</a>
<li><a href="s7-ffi.html#notify">notification in C that a Scheme variable has been set!</a>
<li><a href="s7-ffi.html#namespace">Load C defined stuff into a separate namespace</a>
<li><a href="s7-ffi.html#Cerrors">Error handling in C</a>
<li><a href="s7-ffi.html#testhook">Hooks in C and Scheme</a>
<li><a href="s7-ffi.html#dload">Load a C module dynamically</a>
<li><a href="s7-ffi.html#gmpex">gmp and friends</a>
<li><a href="s7-ffi.html#gdb">gdb</a>
<li><a href="s7-ffi.html#webassembly">WASM</a>
<li><a href="s7-ffi.html#ffinotes">FFI notes</a>
</ul>
<p>s7 exists only to serve as an extension of some other application, so
it is primarily a foreign function interface. s7.h has lots of comments about the individual
functions. Here I'll collect some complete examples. s7.c depends on the following
compile-time flags:
</p>
<pre class="indented">
SIZEOF_VOID_P 8 (default) or 4.
WITH_GMP 1 if you want multiprecision arithmetic (requires gmp, mpfr, and mpc, default is 0)
HAVE_COMPLEX_NUMBERS 1 if your compiler supports complex numbers
HAVE_COMPLEX_TRIG 1 if your math library has complex versions of the trig functions
DISABLE_DEPRECATED 1 if you want to make sure you're not using any deprecated s7 stuff (default is 0)
WITH_IMMUTATBLE_UNQUOTE 1 if you want "unquote" omitted (default is 0)
WITH_EXTRA_EXPONENT_MARKERS 1 if you want "d", "f", "l", and "s" in addition to "e" as exponent markers (default is 0)
if someone defends these exponent markers, ask him to read 1l11+11l1i
(in 2 million lines of open-source Scheme, there is not one use of these silly things)
WITH_SYSTEM_EXTRAS 1 if you want some additional OS-related functions built-in (default is 0)
WITH_MAIN 1 if you want s7.c to include a main program section that runs a REPL.
WITH_C_LOADER 1 if you want to be able to load shared object files with load.
</pre>
<p>See the comment at the start of s7.c for more information about these switches.
s7.h defines the two main number types: s7_int and s7_double.
The examples that follow show:
</p>
<ul>
<li><a href="#repl">read-eval-print loop (and emacs)</a>
<li><a href="#defun">define a function with arguments and a returned value, and define a variable </a>
<li><a href="#defvar">call a Scheme function from C, and get/set Scheme variable values in C</a>
<li><a href="#juce">C++ and Juce</a>
<li><a href="#sndlib">load sndlib using the Xen functions and macros</a>
<li><a href="#pwstype">add a new Scheme type and a procedure with a setter</a>
<li><a href="#functionportexample">redirect display output to a C procedure</a>
<li><a href="#extendop">extend a built-in operator ("+" in this case)</a>
<li><a href="#definestar1">C-side define* (s7_define_function_star)</a>
<li><a href="#definemacro1">C-side define-macro (s7_define_macro)</a>
<li><a href="#definegeneric">define a generic function in C</a>
<li><a href="#signal">signal handling (C-C to break out of an infinite loop)</a>
<li><a href="#notify">notification in C that a Scheme variable has been set!</a>
<li><a href="#namespace">Load C defined stuff into a separate namespace</a>
<li><a href="#Cerrors">Error handling in C</a>
<li><a href="#testhook">Hooks in C and Scheme</a>
<li><a href="#dload">Load a C module dynamically</a>
<li><a href="#gmpex">gmp and friends</a>
<li><a href="#gdb">gdb</a>
<li><a href="#webassembly">WASM</a>
</ul>
<div class="header" id="repl"><h4>A simple listener</h4></div>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "s7.h"
int main(int argc, char **argv)
{
s7_scheme *s7 = <em class=red>s7_init</em>(); /* initialize the interpreter */
while (1) /* fire up a read-eval-print loop */
{
char buffer[512];
fprintf(stdout, "\n> "); /* prompt for input */
fgets(buffer, 512, stdin);
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{ /* evaluate the input and print the result */
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
<em class=red>s7_eval_c_string</em>(s7, response);
}}
}
/* if not using gcc or clang, make mus-config.h (it can be empty), then
*
* gcc -c s7.c -I.
* gcc -o repl repl.c s7.o -lm -I. -ldl
*
* run it:
*
* repl
* > (+ 1 2)
* <em class="gray">3</em>
* > (define (add1 x) (+ 1 x))
* <em class="gray">add1</em>
* > (add1 2)
* <em class="gray">3</em>
* > (exit)
*
* for long-term happiness in linux use:
* gcc -o repl repl.c s7.o -Wl,-export-dynamic -lm -I. -ldl
* clang also needs -fPIC I think
* freebsd:
* gcc -o repl repl.c s7.o -Wl,-export-dynamic -lm -I.
* osx:
* gcc -o repl repl.c s7.o -lm -I.
* openbsd:
* clang -o repl repl.c s7.o -I. -fPIC -Wl,-export-dynamic -lm
*/
</pre>
</div>
<p>Since this reads stdin and writes stdout, it can be run as a Scheme subjob of emacs.
One (inconvenient) way to do this is to set the emacs variable scheme-program-name to
the name of the exectuable created above ("repl"), then call the emacs function run-scheme:
M-x eval-expression in emacs, followed by (setq scheme-program-name "repl"), then
M-x run-scheme, and you're talking to s7 in emacs. Of course, this connection can be
customized indefinitely. See, for example, inf-snd.el in the Snd package.
</p>
<p>Here are the not-always-built-in indentations I use in emacs:
</p>
<pre class="indented">
(put 'with-let 'scheme-indent-function 1)
(put 'with-baffle 'scheme-indent-function 0)
(put 'with-sound 'scheme-indent-function 1)
(put 'catch 'scheme-indent-function 1)
(put 'lambda* 'scheme-indent-function 1)
(put 'when 'scheme-indent-function 1)
(put 'let-temporarily 'scheme-indent-function 1)
(put 'let*-temporarily 'scheme-indent-function 1)
(put 'call-with-input-string 'scheme-indent-function 1)
(put 'unless 'scheme-indent-function 1)
(put 'letrec* 'scheme-indent-function 1)
(put 'sublet 'scheme-indent-function 1)
(put 'varlet 'scheme-indent-function 1)
(put 'case* 'scheme-indent-function 1)
(put 'macro 'scheme-indent-function 1)
(put 'macro* 'scheme-indent-function 1)
(put 'bacro 'scheme-indent-function 1)
(put 'bacro* 'scheme-indent-function 1)
</pre>
<p>To read stdin while working in a GUI-based program is trickier. In glib, you can use
something like this:
</p>
<blockquote>
<div class="indented">
<pre>
static gboolean read_stdin(GIOChannel *source, GIOCondition condition, gpointer data)
{
/* here read from g_io_channel_unix_get_fd(source) and call s7_eval_string */
return(true);
}
/* ... during initialization ... */
GIOChannel *channel;
channel = g_io_channel_unix_new(STDIN_FILENO); /* watch stdin */
stdin_id = g_io_add_watch_full(channel, /* and call read_stdin above if input is noticed */
G_PRIORITY_DEFAULT,
(GIOCondition)(G_IO_IN | G_IO_HUP | G_IO_ERR),
<em class=red>read_stdin</em>, NULL, NULL);
g_io_channel_unref(channel);
</pre></div>
</blockquote>
<p>Here's a version that uses libtecla for the line editor:
</p>
<blockquote>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <libtecla.h>
#include "s7.h"
int main(int argc, char **argv)
{
GetLine *gl = new_GetLine(500, 5000); /* The tecla line editor */
s7_scheme *s7 = s7_init();
while (1)
{
char *buffer;
buffer = gl_get_line(gl, "> ", NULL, 0);
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
s7_eval_c_string(s7, response);
fprintf(stdout, "\n");
}}
gl = del_GetLine(gl);
}
/*
* gcc -c s7.c -I. -O2 -g3
* gcc -o ex1 ex1.c s7.o -lm -I. -ltecla -ldl
*/
</pre></div>
</blockquote>
<p>A repl (based on repl.scm or nrepl.scm) is built into s7. Include the compiler flag -DWITH_MAIN:
</p>
<pre class="indented">
gcc -o nrepl s7.c -O2 -I. -Wl,-export-dynamic -lm -ldl -DWITH_MAIN -DWITH_NOTCURSES -lnotcurses-core
</pre>
<p id="beginhook">
Common Lisp has something called "evalhook" that makes it possible
to insert your own function into the eval loop. In s7, we have a "begin_hook" which sits at the opening of many begin blocks
(implicit or explicit). begin_hook is a (C) function;
if it sets its bool argument to true,
s7 interrupts the current evaluation.
Here is a version of the REPL in which begin_hook watches for C-g to interrupt
some long computation:
</p>
<blockquote>
<div class="indented">
<pre>
/* terminal-based REPL,
* an expansion of the <a href="#repl">read-eval-print loop</a> program above.
* type C-g to interrupt an evaluation.
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include <signal.h>
#include "s7.h"
static struct termios save_buf, buf;
static void sigcatch(int n)
{
/* put things back the way they were */
tcsetattr(fileno(stdin), TCSAFLUSH, &save_buf);
exit(0);
}
static char buffer[512];
static int type_ahead_point = 0;
static void <em class=red>watch_for_c_g</em>(s7_scheme *sc, bool *all_done)
{
char c;
/* watch for C-g without blocking, save other chars as type-ahead */
tcsetattr(fileno(stdin), TCSAFLUSH, &buf);
if (read(fileno(stdin), &c, 1) == 1)
{
if (c == 7) /* C-g */
{
*all_done = true;
type_ahead_point = 0;
}
else buffer[type_ahead_point++] = c;
}
tcsetattr(fileno(stdin), TCSAFLUSH, &save_buf);
}
int main(int argc, char **argv)
{
s7_scheme *s7;
bool use_begin_hook = (tcgetattr(fileno(stdin), &save_buf) >= 0);
if (use_begin_hook)
{
buf = save_buf;
buf.c_lflag &= ~ICANON;
buf.c_cc[VMIN] = 0;
buf.c_cc[VTIME] = 0;
signal(SIGINT, sigcatch);
signal(SIGQUIT, sigcatch);
signal(SIGTERM, sigcatch);
}
s7 = s7_init();
if (argc == 2)
{
fprintf(stderr, "load %s\n", argv[1]);
if (!s7_load(s7, argv[1]))
fprintf(stderr, "can't find %s\n", argv[1]);
}
else
{
while (1)
{
fprintf(stdout, "\n> ");
fgets((char *)(buffer + type_ahead_point), 512 - type_ahead_point, stdin);
type_ahead_point = 0;
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
if (use_begin_hook)
<em class=red>s7_set_begin_hook</em>(s7, watch_for_c_g);
s7_eval_c_string(s7, response);
if (use_begin_hook)
<em class=red>s7_set_begin_hook</em>(s7, NULL);
}}}
if (use_begin_hook)
tcsetattr(fileno(stdin), TCSAFLUSH, &save_buf);
}
</pre></div>
</blockquote>
<div class="header" id="defun"><h4>Define a function with arguments and a returned value, and a variable</h4></div>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "s7.h"
static s7_pointer add1(s7_scheme *sc, s7_pointer args)
{
/* all added functions have this form, args is a list,
* s7_car(args) is the first arg, etc
*/
if (<em class=red>s7_is_integer</em>(s7_car(args)))
return(<em class=red>s7_make_integer</em>(sc, 1 + <em class=red>s7_integer</em>(s7_car(args))));
return(s7_wrong_type_arg_error(sc, "add1", 1, s7_car(args), "an integer"));
}
int main(int argc, char **argv)
{
s7_scheme *s7 = s7_init();
s7_define_function(s7, "add1", add1, 1, 0, false, "(add1 int) adds 1 to int");
/* add the function "add1" to the interpreter.
* 1, 0, false -> one required arg,
* no optional args,
* no "rest" arg
*/
<em class=red>s7_define_variable</em>(s7, "my-pi", <em class=red>s7_make_real</em>(s7, 3.14159265));
while (1) /* fire up a "repl" */
{
char buffer[512];
fprintf(stdout, "\n> "); /* prompt for input */
fgets(buffer, 512, stdin);
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
s7_eval_c_string(s7, response); /* evaluate input and write the result */
}}
}
/* doc7
* > my-pi
* <em class="gray">3.14159265</em>
* > (+ 1 (add1 1))
* <em class="gray">3</em>
* > (exit)
*/
</pre></div>
<div class="header" id="defvar"><h4>Call a Scheme-defined function from C, and get/set Scheme variable values in C</h4></div>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "s7.h"
int main(int argc, char **argv)
{
s7_scheme *s7 = s7_init();
s7_define_variable(s7, "an-integer", s7_make_integer(s7, 1));
s7_eval_c_string(s7, "(define (add1 a) (+ a 1))");
fprintf(stderr, "an-integer: %lld\n",
s7_integer(<em class=red>s7_name_to_value</em>(s7, "an-integer")));
<em class=red>s7_symbol_set_value</em>(s7, <em class=red>s7_make_symbol</em>(s7, "an-integer"), s7_make_integer(s7, 32));
fprintf(stderr, "now an-integer: %lld\n",
s7_integer(<em class=red>s7_name_to_value</em>(s7, "an-integer")));
fprintf(stderr, "(add1 2): %lld\n",
s7_integer(<em class=red>s7_call</em>(s7,
s7_name_to_value(s7, "add1"),
s7_cons(s7, s7_make_integer(s7, 2), s7_nil(s7)))));
}
/*
* doc7
* an-integer: 1
* now an-integer: 32
* (add1 2): 3
*/
</pre>
<p>In more complicated cases, it is probably easier use s7_eval_c_string_with_environment.
As an example, say we want to have a C procedure that calls the pretty printer function pp
in write.scm, returning a string to C. We need to make sure pp is loaded, and catch
any errors that come up. And we need to pass the C-level s7 object to pp. So...
</p>
<pre>
static const char *pp(s7_scheme *sc, s7_pointer obj) /* (pp obj) */
{
return(s7_string(
<em class=red>s7_eval_c_string_with_environment</em>(sc,
"(catch #t \
(lambda () \
(unless (defined? 'pp) \
(load \"write.scm\")) \
(<em class=red>pp</em> obj)) \
(lambda (type info) \
(apply format #f info)))",
<em class=red>s7_inlet</em>(sc, s7_list(sc, 1, s7_cons(sc, s7_make_symbol(sc, "obj"), obj))))));
}
</pre>
<p>and now when we want a pretty-printed representation of something: pp(sc, obj);
The s7_inlet call is creating a local environment with the object "obj" bound
in scheme to the name "obj" so that (pp obj) will find the "obj" that actually
lives in C. You may need to give the full filename for write.scm, or add its path
to the <a href="s7.html#loadpath">load-path list</a>. In the latter case, <code>(require write.scm)</code> could
replace <code>(unless (defined?...))</code>.
</p>
</div>
<div class="header" id="juce"><h4>C++ and Juce, from Rick Taube</h4></div>
<div class="indented">
<pre>
int main(int argc, const char* argv[])
{
initialiseJuce_NonGUI();
s7_scheme *s7 = s7_init();
if (!s7)
{
std::cout << "Can't start S7!\n";
return -1;
}
while (true)
{
s7_pointer val;
std::string str;
std::cout << "\ns7> ";
std::getline(std::cin, str);
val = s7_eval_c_string(s7, str.c_str());
std::cout << s7_object_to_c_string(s7, val);
}
free(s7);
std::cout << "Bye!\n";
return 0;
}
</pre></div>
<div class="header" id="sndlib"><h4>Load sndlib into an s7 repl</h4></div>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
/* assume we've configured and built sndlib, so it has created a mus-config.h file.
* also assume we've built s7 with WITH_SYSTEM_EXTRAS set, so we have file-exists? and delete-file
*/
#include "mus-config.h"
#include "s7.h"
#include "xen.h"
#include "clm.h"
#include "clm2xen.h"
/* we need to redirect clm's mus_error calls to s7_error */
static void mus_error_to_s7(int type, char *msg)
{
s7_error(s7, /* s7 is declared in xen.h, defined in xen.c */
s7_make_symbol(s7, "mus-error"),
s7_cons(s7, s7_make_string(s7, msg), s7_nil(s7)));
}
int main(int argc, char **argv)
{
s7 = s7_init(); /* initialize the interpreter */
s7_xen_initialize(s7); /* initialize the xen stuff (hooks and the xen s7 FFI used by sndlib) */
Init_sndlib(); /* initialize sndlib with all the functions linked into s7 */
mus_error_set_handler(mus_error_to_s7); /* catch low-level errors and pass them to s7-error */
while (1) /* fire up a "repl" */
{
char buffer[512];
fprintf(stdout, "\n> "); /* prompt for input */
fgets(buffer, 512, stdin);
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
s7_eval_c_string(s7, response); /* evaluate input and write the result */
}}
}
/* gcc -o doc7 doc7.c -lm -I. /usr/local/lib/libsndlib.a -lasound -ldl
*
* (load "sndlib-ws.scm")
* (with-sound () (outa 10 .1))
* (load "v.scm")
* (with-sound () (fm-violin 0 .1 440 .1))
*
* you might also need -lgsl -lgslcblas -lfftw3
*/
</pre>
</div>
<p>If you built libsndlib.so, it is possible to use it directly in the s7 repl:
</p>
<pre>
repl ; this is a bare s7 running repl.scm via -DWITH_MAIN=1
loading libc_s7.so
> (load "/home/bil/test/sndlib/libsndlib.so" (inlet 'init_func 's7_init_sndlib))
#t ; s7_init_sndlib ties all the sndlib functions and variables into s7
> (load "sndlib-ws.scm")
tmpnam
> (set! *clm-player* (lambda (file) (system (format #f "sndplay ~A" file))))
> (load "v.scm")
fm-violin
> (with-sound (:play #t) (fm-violin 0 1 440 .1))
"test.snd"
</pre>
<p>You can use autoload to load libsndlib when needed:
</p>
<pre class="indented">
(define (find-library name)
(if (or (file-exists? name)
(char=? (name 0) #\/))
name
(call-with-exit
(lambda (return)
(for-each
(lambda (path)
(let ((new-name (string-append path "/" name)))
(if (file-exists? new-name)
(return new-name))))
*load-path*)
(let ((libs (getenv "LD_LIBRARY_PATH")) ; colon separated directory names
(start 0))
(do ((colon (char-position #\: libs) (char-position #\: libs start)))
((or (not colon)
(let ((new-name (string-append (substring libs start colon) "/" name)))
(and (file-exists? new-name)
(return new-name)))))
(set! start (+ colon 1))))
name))))
(<em class=red>autoload</em> 'clm
(lambda (e)
(load (find-library "libsndlib.so") (inlet '(init_func . s7_init_sndlib)))
(set! *features* (cons 'clm *features*))
(with-let (rootlet) (define clm #t))
(load "sndlib-ws.scm")
(set! *clm-player* (lambda (file) (system (format #f "sndplay ~A" file))))))
</pre>
<p>and use the repl's vt100 stuff to (for example) post the current begin time
as a note list computes:
</p>
<pre class="indented">
(define (clm-notehook . args)
;; assume second arg is begin time (first is instrument name)
(when (and (pair? args)
(pair? (cdr args))
(number? (cadr args)))
(with-let (sublet (*repl* 'repl-let) :begin-time (cadr args))
(let ((coords (cursor-coords))
(col (floor (/ last-col 2))))
(let ((str (number->string begin-time)))
(format *stderr* "~C[~D;~DH" #\escape prompt-row col)
(format *stderr* "~C[K~A" #\escape (if (> (length str) col) (substring str 0 (- col 1)) str)))
(format *stderr* "~C[~D;~DH" #\escape (cdr coords) (car coords))))))
(set! *clm-notehook* clm-notehook)
</pre>
<div class="header" id="pwstype"><h4>Add a new Scheme type and a procedure with a setter</h4></div>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "s7.h"
/* define *listener-prompt* in scheme, add two accessors for C get/set */
static const char *listener_prompt(s7_scheme *sc)
{
return(s7_string(s7_name_to_value(sc, "*listener-prompt*")));
}
static void set_listener_prompt(s7_scheme *sc, const char *new_prompt)
{
s7_symbol_set_value(sc, s7_make_symbol(sc, "*listener-prompt*"), s7_make_string(sc, new_prompt));
}
/* now add a new type, a struct named "dax" with two fields, a real "x" and a list "data" */
/* since the data field is an s7 object, we'll need to mark it to protect it from the GC */
typedef struct {
s7_double x;
s7_pointer data;
} dax;
static int dax_type_tag = 0;
static s7_pointer dax_to_string(s7_scheme *sc, s7_pointer args)
{
s7_pointer result;
dax *o = (dax *)s7_c_object_value(s7_car(args));
char *data_str = s7_object_to_c_string(sc, o->data);
int data_str_len = strlen(data_str);
char *str = (char *)calloc(data_str_len + 32, sizeof(char));
snprintf(str, data_str_len + 32, "<dax %.3f %s>", o->x, data_str);
free(data_str);
result = s7_make_string(sc, str);
free(str);
return(result);
}
static s7_pointer free_dax(s7_scheme *sc, s7_pointer obj)
{
free(s7_c_object_value(obj));
return(NULL);
}
static s7_pointer mark_dax(s7_scheme *sc, s7_pointer obj)
{
dax *o = (dax *)s7_c_object_value(obj);
s7_mark(o->data);
return(NULL);
}
static s7_pointer make_dax(s7_scheme *sc, s7_pointer args)
{
dax *o = (dax *)malloc(sizeof(dax));
o->x = s7_real(s7_car(args));
if (s7_cdr(args) != s7_nil(sc))
o->data = s7_cadr(args);
else o->data = s7_nil(sc);
return(<em class=red>s7_make_c_object</em>(sc, dax_type_tag, (void *)o));
}
static s7_pointer is_dax(s7_scheme *sc, s7_pointer args)
{
return(s7_make_boolean(sc,
<em class=red>s7_is_c_object</em>(s7_car(args)) &&
<em class=red>s7_c_object_type</em>(s7_car(args)) == dax_type_tag));
}
static s7_pointer dax_x(s7_scheme *sc, s7_pointer args)
{
dax *o = (dax *)<em class=red>s7_c_object_value</em>(s7_car(args));
return(s7_make_real(sc, o->x));
}
static s7_pointer set_dax_x(s7_scheme *sc, s7_pointer args)
{
dax *o = (dax *)s7_c_object_value(s7_car(args));
o->x = s7_real(s7_cadr(args));
return(s7_cadr(args));
}
static s7_pointer dax_data(s7_scheme *sc, s7_pointer args)
{
dax *o = (dax *)s7_c_object_value(s7_car(args));
return(o->data);
}
static s7_pointer set_dax_data(s7_scheme *sc, s7_pointer args)
{
dax *o = (dax *)s7_c_object_value(s7_car(args));
o->data = s7_cadr(args);
return(o->data);
}
static s7_pointer dax_is_equal(s7_scheme *sc, s7_pointer args)
{
dax *d1, *d2;
s7_pointer p1 = s7_car(args);
s7_pointer p2 = s7_cadr(args);
if (p1 == p2)
return(s7_t(sc));
if ((!s7_is_c_object(p2)) ||
(s7_c_object_type(p2) != dax_type_tag))
return(s7_f(sc));
d1 = (dax *)s7_c_object_value(p1);
d2 = (dax *)s7_c_object_value(p2);
return(s7_make_boolean(sc,
(d1->x == d2->x) &&
(s7_is_equal(sc, d1->data, d2->data))));
}
int main(int argc, char **argv)
{
s7_scheme *s7 = s7_init();
s7_define_variable(s7, "*listener-prompt*", s7_make_string(s7, ">"));
dax_type_tag = <em class=red>s7_make_c_type</em>(s7, "dax");
s7_c_type_set_gc_free(s7, dax_type_tag, free_dax);
s7_c_type_set_gc_mark(s7, dax_type_tag, mark_dax);
s7_c_type_set_is_equal(s7, dax_type_tag, dax_is_equal);
s7_c_type_set_to_string(s7, dax_type_tag, dax_to_string);
s7_define_function(s7, "make-dax", make_dax, 2, 0, false, "(make-dax x data) makes a new dax");
s7_define_function(s7, "dax?", is_dax, 1, 0, false, "(dax? anything) returns #t if its argument is a dax object");
s7_define_variable(s7, "dax-x",
<em class=red>s7_dilambda</em>(s7, "dax-x", dax_x, 1, 0, set_dax_x, 2, 0, "dax x field"));
s7_define_variable(s7, "dax-data",
<em class=red>s7_dilambda</em>(s7, "dax-data", dax_data, 1, 0, set_dax_data, 2, 0, "dax data field"));
while (1)
{
char buffer[512];
fprintf(stdout, "\n%s ", listener_prompt(s7));
fgets(buffer, 512, stdin);
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
s7_eval_c_string(s7, response); /* evaluate input and write the result */
}}
}
/* (in Linux);
* gcc dax.c -o dax -I. -O2 -g s7.o -ldl -lm -Wl,-export-dynamic -Wno-stringop-overflow
* dax
* > *listener-prompt*
* <em class="gray">">"</em>
* > (set! *listener-prompt* ":")
* <em class="gray">":"</em>
* : (define obj (make-dax 1.0 (list 1 2 3)))
* <em class="gray">obj</em>
* : obj
* <em class="gray">#<dax 1.000 (1 2 3)></em>
* : (dax-x obj)
* <em class="gray">1.0</em>
* : (dax-data obj)
* <em class="gray">(1 2 3)</em>
* : (set! (dax-x obj) 123.0)
* <em class="gray">123.0</em>
* : obj
* <em class="gray">#<dax 123.000 (1 2 3)></em>
* : (dax? obj)
* <em class="gray">#t</em>
* : (exit)
*/
</pre></div>
<div class="header" id="functionportexample"><h4>Redirect output (and input) to a C procedure</h4></div>
<div class="indented">
<pre>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "s7.h"
static void my_print(s7_scheme *sc, uint8_t c, s7_pointer port)
{
fprintf(stderr, "[%c] ", c);
}
static s7_pointer my_read(s7_scheme *sc, s7_read_t peek, s7_pointer port)
{
return(<em class=red>s7_make_character</em>(sc, fgetc(stdin)));
}
int main(int argc, char **argv)
{
s7_scheme *s7 = s7_init();
<em class=red>s7_set_current_output_port</em>(s7, <em class=red>s7_open_output_function</em>(s7, my_print));
s7_define_variable(s7, "io-port", <em class=red>s7_open_input_function</em>(s7, my_read));
while (1)
{
char buffer[512];
fprintf(stdout, "\n> ");
fgets(buffer, 512, stdin);
if ((buffer[0] != '\n') ||
(strlen(buffer) > 1))
{
char response[1024];
snprintf(response, 1024, "(write %s)", buffer);
s7_eval_c_string(s7, response);
}}
}
/*
* > (+ 1 2)
* <em class="gray">[3]</em>
* > (display "hiho")
* <em class="gray">[h] [i] [h] [o] [#] [<] [u] [n] [s] [p] [e] [c] [i] [f] [i] [e] [d] [>] </em>
* > (define (add1 x) (+ 1 x))
* <em class="gray">[a] [d] [d] [1] </em>
* > (add1 123)