From 6b08e86c9a16bfac5a208a04926dcc66b861a096 Mon Sep 17 00:00:00 2001
From: Aleksey Veresov <aleksey@veresov.pro>
Date: Mon, 28 Sep 2020 04:59:07 +0300
Subject: Something...

---
 src/csx.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)
 create mode 100644 src/csx.c

(limited to 'src')

diff --git a/src/csx.c b/src/csx.c
new file mode 100644
index 0000000..b6b0d38
--- /dev/null
+++ b/src/csx.c
@@ -0,0 +1,167 @@
+#include "csx.h"
+
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+
+
+enum { type_nil, type_pair, type_string, type_atom, type_fn };
+static int  *type(char *p)         { return (int *) (p - sizeof(int)); }
+static void  type_shift(void *p)  { *(char **)p += sizeof(int); }
+static void *type_alloc(int t, int content_size)
+{
+    int *res = malloc(sizeof(int) + content_size);
+    *res     = t;
+    type_shift(&res);
+    return res;
+}
+
+
+struct deflist {
+    char *atom;
+    void *data;
+    struct deflist *next;
+};
+
+static struct state {
+    struct deflist *atoms;
+} csx;
+static int csx_to_init = 0;
+
+static void *nil;
+
+
+static void adddef(struct deflist **l, const char *atom, void *data)
+{
+    struct deflist *old = *l;
+    *l = malloc(sizeof(**l));
+    (*l)->next = old;
+    (*l)->atom = scopy(atom);
+    (*l)->data = data;
+}
+
+static void *csx_fn_new(void *fn, void *userdata, int size)
+{
+    void *res = malloc(sizeof(fn) + sizeof(int) + size);
+    *(void **)res = fn;
+    (char *)res += sizeof(fn);
+    *(int *)res = type_fn;
+    typeshift(&res);
+    if (userdata && size) memcpy(res, userdata, size);
+    return res;
+}
+
+static void *define(void *userdata, struct csx_pair *data)
+{  /* TODO! */
+    int t = *type(data);
+    if (t != type_pair) return nil;
+    t = *type(data->car);
+    if (t == type_atom) {
+        struct csx_pair *cdr = data->cdr;
+        if (*type(cdr) != type_pair || *type(cdr->cdr) != type_nil)
+            return nil;
+        return define_constant(data->car, cdr->cdr);
+    }
+    return define_function(data->car, data->cdr);
+}
+
+/* TODO append, cdr, ... */
+
+static void csx_init()
+{
+    if (!csx_to_init) csx_free();
+    csx.atoms = 0;
+
+    nil = type_alloc(type_nil, 0);
+    adddef(csx.atoms, "append", csx_fn_new(append, 0, 0));
+    adddef(csx.atoms, "define", csx_fn_new(define, 0, 0));
+    adddef(csx.atoms, "cdr",    csx_fn_new(cdr,    0, 0));
+    adddef(csx.atoms, "ifx",    csx_fn_new(ifx,    0, 0));
+    adddef(csx.atoms, "not",    csx_fn_new(not,    0, 0));
+}
+
+void csx_free()
+{
+    free(nil);
+    /* free everything allocated */
+    csx_to_init = 0;
+}
+
+
+struct csx_pair *csx_pair_new(void *car, void *cdr)
+{
+    struct csx_pair *res =type_alloc(type_pair, sizeof(*res));
+    res->car = car;
+    res->cdr = cdr;
+    return res;
+}
+
+
+struct csx_pair *csx_list(void *head, ...)
+{
+    struct csx_pair *res;
+    va_list args;
+    if (csx_to_init) csx_init();
+    if (!head) return nil;
+
+    res = csx_pair_new(head, nil);
+    va_start(args, head);
+    for (head = va_arg(args, void *); head; head = va_arg(args, void *)) {
+        res->cdr = csx_pair_new(head, nil);
+    }
+    va_end(args);
+    return res;
+}
+
+char *csx_string(const char *string)
+{
+    int   strsize;
+    void *res;
+    if (csx_to_init) csx_init();
+    strsize = strlen(string) + 1;
+    res     = type_alloc(type_string, strsize);
+    memcpy(res, string, strsize);
+    return res;
+}
+
+char *csx_atom(const char *name)
+{
+    int   namesize;
+    void *res;
+    if (csx_to_init) csx_init();
+    namesize = strlen(name) + 1;
+    res      = type_alloc(type_atom, namesize);
+    memcpy(res, name, namesize);
+    return res;
+}
+
+
+static void *lookup(struct deflist *d, char *atom)
+{
+    if (!d) return nil;
+    if (!strcmp(d->atom, atom)) return d->data;
+    return lookup(d->next, atom);
+}
+
+void *eval_fn(void *fn, void *args)
+{  /* TODO! */
+    /* function : type :> userdata */
+    return 0;
+}
+
+static void *eval_pair(struct csx_pair *pair)
+{
+    void *fn;
+    int t = *type(pair->car);
+    if (t == type_fn) fn = pair->car;
+    else              fn = csx_evaluate(pair->car);
+    return eval_fn(fn, pair->cdr);
+}
+
+void *csx_evaluate(void *expression)
+{
+    int t = *type(expression);
+    if (t == type_atom) return lookup(csx.atoms, expression);
+    if (t != type_pair) return nil;
+    return eval_pair(expression);
+}
-- 
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