Add primitive procedures to expression type

lib/include/expr.h

@@ -7,15 +7,21 @@
 #include <stddef.h>
 #include <stdint.h>
 
+struct am;
+struct store;
+
 typedef struct {
 	char buf[MAX_SYMBOL_LEN];
 	size_t len;
 } symbol_t;
 
+typedef void (*prim_proc_t)(struct am *am, struct store *store);
+
 typedef enum {
 	ATOM_TYPE_EMPTY_LIST,
 	ATOM_TYPE_INTEGER,
 	ATOM_TYPE_SYMBOL,
+	ATOM_TYPE_PRIM_PROC,
 } atom_type_t;
 
 typedef struct {
@@ -23,6 +29,7 @@ typedef struct {
 	union {
 		int64_t integer;
 		symbol_t symbol;
+		prim_proc_t prim_proc;
 	};
 } atom_t;
 
@@ -40,12 +47,11 @@ typedef struct expr {
 	};
 } expr_t;
 
-struct store;
-
 expr_t *expr_integer(struct store *store, int64_t value);
 expr_t *expr_symbol(struct store *store, const symbol_t *symbol);
 expr_t *expr_str_symbol(struct store *store, const char *str);
 expr_t *expr_empty_list(struct store *store);
 expr_t *expr_pair(struct store *store, expr_t *car, expr_t *cdr);
+expr_t *expr_prim_proc(struct store *store, prim_proc_t prim_proc);
 
 #endif