T_VAR

common.h

@@ -34,6 +34,7 @@ extern uint32_t next_cell;
 #define T_FUNC   6  /* function, a.k.a. closure */
 #define T_VECT   7  /* vector */
 #define T_CHAR   8  /* character */
+#define T_VAR    9  /* reference to a lexical variable */
 
 /* true for builtin, as opposed to lambda-defined, functions */
 #define BLTIN_MASK 16
@@ -51,6 +52,9 @@ extern uint32_t next_cell;
 #define CHAR_VALUE(i) (unsigned char)(cells[i] >> 32)
 #define INT32_VALUE(i) (int32_t)(cells[i] >> 32)
 
+#define VAR_FRAME(i) (uint32_t)((cells[i] >> 32) & 0xFFFF)
+#define VAR_SLOT(i) (uint32_t)((cells[i] >> 32) >> 16)
+
 #define LIST_LIKE(i) (TYPE(i) == T_PAIR || i == C_EMPTY)
 
 typedef uint32_t (*builtin_t)(uint32_t);

sketch.c

@@ -130,6 +130,15 @@ uint32_t store_int32(int32_t num) {
   return index;
 }
 
+uint32_t store_var(uint32_t slot, uint32_t frame) {
+  uint64_t value = T_VAR;
+  CHECK_CELLS(1);
+  uint32_t index = next_cell;
+  cells[next_cell++] = value | ((uint64_t)frame << 32) |
+                         (uint64_t)slot << 48;
+  return index;
+}
+
 /* helper func to read a #(...) literal vector */
 int read_vector(char **pstr, uint32_t *pindex) {
   uint32_t initial_indices[2];
@@ -369,6 +378,9 @@ void dump_value(uint32_t index, int implicit_paren) {
       else if (c == '\n') printf("newline");
       else putchar(c);
       break;
+    case T_VAR:
+      printf("#<var:%u,%u>", VAR_SLOT(index), VAR_FRAME(index));
+      break;
     default:
       break;
   }