Make del dict[value] work

Delete a dictionary entry.

Signed-off-by: Keith Packard <keithp@keithp.com>

snek-code.c

@@ -1140,6 +1140,25 @@ snek_code_run(snek_code_t *code_in)
 				ip += sizeof (snek_id_t);
 				snek_frame_mark_global(id);
 				break;
+			case snek_op_del:
+				memcpy(&id, &snek_code->code[ip], sizeof (snek_id_t));
+				ip += sizeof (snek_id_t);
+				if (id == SNEK_ID_NONE) {
+					snek_poly_t lp = snek_stack_pop();
+
+					snek_list_t *l;
+					if (snek_poly_type(lp) != snek_list ||
+					    snek_list_type(l = snek_poly_to_list(lp)) != snek_list_dict)
+					{
+						snek_error_type_1(lp);
+					} else {
+						snek_list_del(l, snek_a);
+						snek_a = SNEK_NULL;
+					}
+				} else {
+					snek_id_del(id);
+				}
+				break;
 			case snek_op_branch:
 				memcpy(&ip, &snek_code->code[ip], sizeof (snek_offset_t));
 				break;

snek-gram.ll

@@ -54,12 +54,21 @@ command		: @{ snek_print_val = snek_interactive; }@ stat
 				if (ref)
 					*ref = poly;
 			}@
-		| DEL NAME
+		| DEL del dels-p
+		| IMPORT NAME
+		;
+dels-p		: COMMA del
+		  dels-p
+		|
+		;
+del		: expr-array
 			@{
-				if (!snek_id_del(snek_token_val.id))
-					snek_undefined(snek_token_val.id);
+				snek_token_val.op = snek_op_del;
+				goto extract_lvalue;
+			}@
+			@{
+				goto add_op_lvalue;
 			}@
-		| IMPORT NAME
 		;
 opt-formals	: formals
 		|
@@ -112,6 +121,7 @@ assign-expr	: expr assign-expr-p
 		;
 assign-expr-p	: ASSIGN
 			@{
+			extract_lvalue:
 				snek_print_val = false;
 				snek_offset_t prev_offset = snek_code_prev_insn();
 				uint8_t *prev = snek_code_at(prev_offset);
@@ -125,7 +135,8 @@ assign-expr-p	: ASSIGN
 					memcpy(&id, prev + 1, sizeof (snek_id_t));
 					break;
 				case snek_op_array:
-					snek_code_set_push(snek_code_prev_prev_insn());
+					if (snek_token_val.op != snek_op_del)
+						snek_code_set_push(snek_code_prev_prev_insn());
 					id = SNEK_ID_NONE;
 					break;
 				default:
@@ -141,6 +152,7 @@ assign-expr-p	: ASSIGN
 			}@
 		  expr
 			@{
+			add_op_lvalue:;
 				snek_op_t op = value_pop().offset;
 				snek_id_t id = value_pop().id;
 

snek-list.c

@@ -194,7 +194,19 @@ snek_list_get(snek_list_t *list, snek_poly_t p, bool report_error)
 	snek_poly_t *r = _snek_list_ref(list, p, report_error, false);
 	if (r)
 		return *r;
-	return SNEK_ZERO;
+	return SNEK_NULL;
+}
+
+void
+snek_list_del(snek_list_t *list, snek_poly_t p)
+{
+	snek_poly_t *r = snek_list_ref(list, p, true);
+	if (!r)
+		return;
+	r--;
+	snek_offset_t remain = snek_list_data(list) + list->size - r;
+	memmove(r, r+2, (remain - 2) * sizeof (snek_poly_t));
+	list->size -= 2;
 }
 
 int8_t

snek.h

@@ -137,6 +137,7 @@ typedef enum {
 	snek_op_slice,
 
 	snek_op_global,
+	snek_op_del,
 
 	snek_op_branch,
 	snek_op_branch_true,
@@ -581,6 +582,9 @@ snek_list_get(snek_list_t *list, snek_poly_t p, bool report_error);
 snek_poly_t *
 snek_list_data(snek_list_t *list);
 
+void
+snek_list_del(snek_list_t *list, snek_poly_t p);
+
 int8_t
 snek_list_cmp(snek_list_t *a, snek_list_t *b);
 

test/dict.py

@@ -67,3 +67,9 @@ def check(expect,got,which):
 
 check(7, a[6], "a[6] == 7")
 check("g", b["f"], "b['f'] == 'g'")
+
+del a[1]
+del b['c']
+
+check({3:4, 6:7}, a, "a = {3:4, 6:7}")
+check({'a': 'e', 'f': 'g'}, b, "b = {'a': 'e', 'f': 'g'}")