Constructors and context -> sys

We can register memory we've allocated onto the heap into a ~sys_t~
instance for examination (read: garbage collection) later.  We can
also add items to the symbol table it has internally.

constructor.c

@@ -0,0 +1,48 @@
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the Unlicense for details.
+
+ * You may distribute and modify this code under the terms of the Unlicense,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-20
+ * Description: Lisp constructors/destructors
+ */
+
+#include <malloc.h>
+
+#include "./base.h"
+
+lisp_t *make_int(i64 i)
+{
+  return tag_int(i);
+}
+
+lisp_t *cons(sys_t *sys, lisp_t *car, lisp_t *cdr)
+{
+  cons_t *cons = calloc(1, sizeof(*cons));
+  cons->car    = car;
+  cons->cdr    = cdr;
+
+  lisp_t *lcons = tag_cons(cons);
+  sys_register(sys, lcons);
+  return lcons;
+}
+
+lisp_t *make_vec(sys_t *sys, u64 capacity)
+{
+  lvec_t *lvec = calloc(1, sizeof(*lvec));
+  vec_make(&lvec->data, capacity);
+  lisp_t *ptr = tag_vec(lvec);
+  sys_register(sys, ptr);
+  return ptr;
+}
+
+lisp_t *intern(sys_t *sys, sv_t sv)
+{
+  char *s = sym_table_find(&sys->symtable, sv);
+  return tag_sym(s);
+}