add array index setting syntax

1 files changed, 29 insertions, 14 deletions

diff --git a/com.c b/com.c
index ff13815..521adec 100644
--- a/com.c
+++ b/com.c
@@ -59,12 +59,15 @@ static int stack_effect_of(Op opcode) {
 	case OP_MOD:
 	case OP_ARRAPPEND:
 		return -1;
+	case OP_SETIDX:
+		return -2;
 
 	// these ones depend on their argument. handle them specifically
 	case OP_CALL:
 	case OP_TAILCALL:
 	case OP_ENDSCOPE:
 		return 0;
+
 	default:
 		ERROR("unknown stack effect of opcode %d",opcode); 
 	}
@@ -172,21 +175,31 @@ void single_form(Compiler *C, AstVec l, Op op) {
 static Local *locate_local(Compiler *C, char *name);
 
 void set_form(Compiler *C, AstVec l, Op _, int flags) {
-	AstNode ident = l.vals[1];
-	CHECK(ident.ty == AST_IDENT, "set's first argument must be identifier");
-	char *name = ident.as.str;
-
-	Local *loc = locate_local(C, name);
-	if (loc != NULL) {
-		compile_node(C, l.vals[2], 0);
-		compile_opcode(C, OP_SETLOCAL);
-		compile_byte(C, loc->slot);
-	} else {
-		// write global
-		ObjString *o = objstring_copy_cstr(C->S, name);
+	AstNode target = l.vals[1];
+	if (target.ty == AST_IDENT)  {
+		// set variable, local or global
+		char *name = target.as.str;
+
+		Local *loc = locate_local(C, name);
+		if (loc != NULL) {
+			compile_node(C, l.vals[2], 0);
+			compile_opcode(C, OP_SETLOCAL);
+			compile_byte(C, loc->slot);
+		} else {
+			// write global
+			ObjString *o = objstring_copy_cstr(C->S, name);
+			compile_node(C, l.vals[2], 0);
+			compile_opcode(C, OP_SETGLOBAL);
+			compile_byte(C, compile_constant(C, VAL_OBJ(o)));
+		}
+	} else if (target.ty == AST_LIST) {
+		AstVec pair = target.as.list;
+		CHECK(pair.len == 2, "can only set to (arr, ix) 2-pair");
+		// (value arr ix) <- TOS
 		compile_node(C, l.vals[2], 0);
-		compile_opcode(C, OP_SETGLOBAL);
-		compile_byte(C, compile_constant(C, VAL_OBJ(o)));
+		compile_node(C, pair.vals[0], 0);
+		compile_node(C, pair.vals[1], 0);
+		compile_opcode(C, OP_SETIDX);
 	}
 }
 
@@ -332,6 +345,8 @@ void def_form(Compiler *C, AstVec l, Op _, int flags) {
 	compile_node(C, l.vals[2], 0);
 	declare_local(C, l.vals[1].as.str);
 	// whatever is calling us will compile an OP_DROP next
+	// or, well. not if we're in tail position. but i can't see
+	// any circumstance where you'd want that anyway
 	compile_opcode(C, OP_NIL);
 }