Implement else

cesanta · May 4, 2021 · ecae62c · ecae62c
1 parent 598b7b4
commit ecae62c
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Showing 3 changed files with 21 additions and 5 deletions.
diff --git a/README.md b/README.md
@@ -71,7 +71,7 @@ int main(void) {
 - No `!=`, `==`. Use `!==`, `===`
 - No `var`, no `const`. Use `let`. Strict mode only
 - No `do`, `switch`, `for`. Use `while`
-- No `else`, only `if`. No ternary operator `a ? b : c`
+- No ternary operator `a ? b : c`
 - No arrays, closures, prototypes, `this`, `new`, `delete`, `instanceof`
 - No standard library: no `Date`, `Regexp`, `Function`, `String`, `Number`
 - Strings are binary data chunks, not Unicode strings

diff --git a/elk.c b/elk.c
@@ -1104,11 +1104,18 @@ static jsval_t js_if(struct js *js) {
   if (next(js) != TOK_LPAREN) return js_err(js, "parse error");
   jsval_t cond = js_expr(js, TOK_RPAREN, TOK_EOF);
   if (js->tok != TOK_RPAREN) return js_err(js, "parse error");
-  uint8_t flags = js->flags;
+  bool noexec = js->flags & F_NOEXEC;
   bool cond_true = js_truthy(js, cond);
   if (!cond_true) js->flags |= F_NOEXEC;
   jsval_t res = js_block_or_stmt(js);
-  if (!cond_true && !(flags & F_NOEXEC)) js->flags &= ~F_NOEXEC;
+  if (!cond_true && !noexec) js->flags &= ~F_NOEXEC;
+  if (lookahead(js) == TOK_ELSE) {
+    next(js);
+    if (cond_true) js->flags |= F_NOEXEC;
+    res = js_block_or_stmt(js);
+    if (cond_true && !noexec) js->flags &= ~F_NOEXEC;
+  }
+  // printf("IF: else %d\n", lookahead(js) == TOK_ELSE);
   return res;
 }
 
@@ -1158,8 +1165,8 @@ static jsval_t js_stmt(struct js *js, uint8_t etok) {
     case TOK_CASE: case TOK_CATCH: case TOK_CLASS: case TOK_CONST:
     case TOK_DEFAULT: case TOK_DELETE: case TOK_DO: case TOK_FINALLY:
     case TOK_FOR: case TOK_IN: case TOK_INSTANCEOF: case TOK_NEW:
-    case TOK_ELSE: case TOK_SWITCH: case  TOK_THIS: case TOK_THROW:
-    case TOK_TRY: case TOK_VAR: case TOK_VOID: case TOK_WITH: case TOK_YIELD:
+    case TOK_SWITCH: case  TOK_THIS: case TOK_THROW: case TOK_TRY:
+    case TOK_VAR: case TOK_VOID: case TOK_WITH: case TOK_YIELD:
       return js_err(js, "'%.*s' not implemented", (int) js->tlen, js->code + js->toff);
     case TOK_CONTINUE:  return js_continue(js);
     case TOK_BREAK:     return js_break(js);

diff --git a/test/unit_test.c b/test/unit_test.c
@@ -234,6 +234,15 @@ static void test_flow(void) {
   assert(ev(js, "a = b = 0; while (b++ < 10) while (a < b) a++; a", "10"));
   assert(ev(js, "a = 0; while (1) { if (a++ < 10) continue; break;} a", "11"));
   assert(ev(js, "a=b=0; while (b++<10) {true;a++;} a", "10"));
+  assert(ev(js, "a=b=0; if (false) b++; else b--; b", "-1"));
+  assert(ev(js, "a=b=0; if (false) {b++;} else {b--;} b", "-1"));
+  assert(ev(js, "a=b=0; if (false) {2;b++;} else {2;b--;} b", "-1"));
+  assert(ev(js, "a=b=0; if (true) b++; else b--; b", "1"));
+  assert(ev(js, "a=b=0; if (true) {2;b++;} else {2;b--;} b", "1"));
+  assert(ev(js, "a=0; if (1) a=1; else if (0) a=2; a;", "1"));
+  assert(ev(js, "a=0; if (0) a=1; else if (1) a=2; a;", "2"));
+  assert(ev(js, "a=0; if (0){7;a=1;}else if (1){7;a=2;} a;", "2"));
+  assert(ev(js, "a=0; if(0){7;a=1;}else if(0){5;a=2;}else{3;a=3;} a;", "3"));
 }
 
 static void test_scopes(void) {