feat($parse): support the ternary/conditional operator

Closes #272
dart-archive · Nov 21, 2013 · e38da6f · e38da6f
1 parent 0f8bb2b
commit e38da6f
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Showing 4 changed files with 122 additions and 10 deletions.
diff --git a/lib/core/parser/backend.dart b/lib/core/parser/backend.dart
@@ -179,6 +179,10 @@ class ParserBackend {
 
   _op(opKey) => OPERATORS[opKey];
 
+  Expression ternaryFn(Expression cond, Expression _true, Expression _false) =>
+      new Expression((self, [locals]) => _op('?')(
+          self, locals, cond, _true, _false));
+
   Expression binaryFn(Expression left, String op, Expression right) =>
       new Expression((self, [locals]) => _op(op)(self, locals, left, right));
 

diff --git a/lib/core/parser/parser.dart b/lib/core/parser/parser.dart
@@ -128,7 +128,8 @@ Map<String, Operator> OPERATORS = {
   '||': (s, l, a, b) => toBool(a.eval(s, l)) || toBool(b.eval(s, l)),
   '&': (s, l, a, b) => a.eval(s, l) & b.eval(s, l),
   '|': NOT_IMPL_OP, //b(locals)(locals, a(locals))
-  '!': (self, locals, a, b) => !toBool(a.eval(self, locals))
+  '!': (s, l, a, b) => !toBool(a.eval(s, l)),
+  '?': (s, l, c, t, f) => toBool(c.eval(s, l)) ? t.eval(s, l) : f.eval(s, l),
 };
 
 class DynamicParser implements Parser {
@@ -343,17 +344,34 @@ class DynamicParser implements Parser {
     }
   }
 
+  ParserAST _ternary() {
+    var ts = _saveTokens();
+    var cond = _logicalOR();
+    var token = _expect('?');
+    if (token != null) {
+      var _true = _expression();
+      if ((token = _expect(':')) != null) {
+        cond = _b.ternaryFn(cond, _true, _expression());
+      } else {
+        throw _parserError('Conditional expression ${_tokensText(ts)} requires '
+                           'all 3 expressions');
+      }
+    }
+    _stopSavingTokens(ts);
+    return cond;
+  }
+
   ParserAST _assignment() {
     var ts = _saveTokens();
-    var left = _logicalOR();
+    var left = _ternary();
     _stopSavingTokens(ts);
     var right;
     var token;
     if ((token = _expect('=')) != null) {
       if (!left.assignable) {
         throw _parserError('Expression ${_tokensText(ts)} is not assignable', token);
       }
-      right = _logicalOR();
+      right = _ternary();
       return _b.assignment(left, right, _evalError);
     } else {
       return left;

diff --git a/test/core/parser/lexer_spec.dart b/test/core/parser/lexer_spec.dart
@@ -237,11 +237,5 @@ main() {
         lex("'\\u1''bla'");
       }).toThrow("Lexer Error: Invalid unicode escape [\\u1''b] at column 2 in expression ['\\u1''bla']");
     });
-
-    it('should throw error on unexpected characters', () {
-      expect(() {
-        lex("a == b ? 3 : 4");
-      }).toThrow('Lexer Error: Unexpected next character [?] at column 7 in expression [a == b ? 3 : 4]');
-    });
   });
 }
diff --git a/test/core/parser/parser_spec.dart b/test/core/parser/parser_spec.dart
@@ -35,6 +35,8 @@ class InheritedMapData extends MapData {
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
+toBool(x) => (x is num) ? x != 0 : x == true;
+
 main() {
   describe('parse', () {
     var scope, parser;
@@ -45,7 +47,7 @@ main() {
     beforeEach(inject((Parser injectedParser) {
       parser = injectedParser;
     }));
-    
+
     eval(String text) => parser(text).eval(scope, null);
     expectEval(String expr) => expect(() => eval(expr));
 
@@ -105,6 +107,24 @@ main() {
       });
 
 
+      it('should parse ternary/conditional expressions', () {
+        var a, b, c;
+        expect(eval("7==3+4?10:20")).toEqual(true?10:20);
+        expect(eval("false?10:20")).toEqual(false?10:20);
+        expect(eval("5?10:20")).toEqual(toBool(5)?10:20);
+        expect(eval("null?10:20")).toEqual(toBool(null)?10:20);
+        expect(eval("true||false?10:20")).toEqual(true||false?10:20);
+        expect(eval("true&&false?10:20")).toEqual(true&&false?10:20);
+        expect(eval("true?a=10:a=20")).toEqual(true?a=10:a=20);
+        expect([scope['a'], a]).toEqual([10, 10]);
+        scope['a'] = a = null;
+        expect(eval("b=true?a=false?11:c=12:a=13")).toEqual(
+                     b=true?a=false?11:c=12:a=13);
+        expect([scope['a'], scope['b'], scope['c']]).toEqual([a, b, c]);
+        expect([a, b, c]).toEqual([12, 12, 12]);
+      });
+
+
       it('should auto convert ints to strings', () {
         expect(eval("'str ' + 4")).toEqual("str 4");
         expect(eval("4 + ' str'")).toEqual("4 str");
@@ -160,6 +180,12 @@ main() {
       });
 
 
+      it('should throw on incorrect ternary operator syntax', () {
+        expectEval("true?1").toThrow(errStr(
+                'Conditional expression true?1 requires all 3 expressions'));
+      });
+
+
       it('should fail gracefully when missing a function', () {
         expect(() {
           parser('doesNotExist()').eval({});
@@ -330,6 +356,76 @@ main() {
       });
 
 
+      it('should parse ternary', () {
+        var returnTrue = scope['returnTrue'] = () => true;
+        var returnFalse = scope['returnFalse'] = () => false;
+        var returnString = scope['returnString'] = () => 'asd';
+        var returnInt = scope['returnInt'] = () => 123;
+        var identity = scope['identity'] = (x) => x;
+        var B = toBool;
+
+        // Simple.
+        expect(eval('0?0:2')).toEqual(B(0)?0:2);
+        expect(eval('1?0:2')).toEqual(B(1)?0:2);
+
+        // Nested on the left.
+        expect(eval('0?0?0:0:2')).toEqual(B(0)?B(0)?0:0:2);
+        expect(eval('1?0?0:0:2')).toEqual(B(1)?B(0)?0:0:2);
+        expect(eval('0?1?0:0:2')).toEqual(B(0)?B(1)?0:0:2);
+        expect(eval('0?0?1:0:2')).toEqual(B(0)?B(0)?1:0:2);
+        expect(eval('0?0?0:2:3')).toEqual(B(0)?B(0)?0:2:3);
+        expect(eval('1?1?0:0:2')).toEqual(B(1)?B(1)?0:0:2);
+        expect(eval('1?1?1:0:2')).toEqual(B(1)?B(1)?1:0:2);
+        expect(eval('1?1?1:2:3')).toEqual(B(1)?B(1)?1:2:3);
+        expect(eval('1?1?1:2:3')).toEqual(B(1)?B(1)?1:2:3);
+
+        // Nested on the right.
+        expect(eval('0?0:0?0:2')).toEqual(B(0)?0:B(0)?0:2);
+        expect(eval('1?0:0?0:2')).toEqual(B(1)?0:B(0)?0:2);
+        expect(eval('0?1:0?0:2')).toEqual(B(0)?1:B(0)?0:2);
+        expect(eval('0?0:1?0:2')).toEqual(B(0)?0:B(1)?0:2);
+        expect(eval('0?0:0?2:3')).toEqual(B(0)?0:B(0)?2:3);
+        expect(eval('1?1:0?0:2')).toEqual(B(1)?1:B(0)?0:2);
+        expect(eval('1?1:1?0:2')).toEqual(B(1)?1:B(1)?0:2);
+        expect(eval('1?1:1?2:3')).toEqual(B(1)?1:B(1)?2:3);
+        expect(eval('1?1:1?2:3')).toEqual(B(1)?1:B(1)?2:3);
+
+        // Precedence with respect to logical operators.
+        expect(eval('0&&1?0:1')).toEqual(B(0)&&B(1)?0:1);
+        expect(eval('1||0?0:0')).toEqual(B(1)||B(0)?0:0);
+
+        expect(eval('0?0&&1:2')).toEqual(B(0)?0&&1:2);
+        expect(eval('0?1&&1:2')).toEqual(B(0)?1&&1:2);
+        expect(eval('0?0||0:1')).toEqual(B(0)?0||0:1);
+        expect(eval('0?0||1:2')).toEqual(B(0)?0||1:2);
+
+        expect(eval('1?0&&1:2')).toEqual(B(1)?B(0)&&B(1):2);
+        expect(eval('1?1&&1:2')).toEqual(B(1)?B(1)&&B(1):2);
+        expect(eval('1?0||0:1')).toEqual(B(1)?B(0)||B(0):1);
+        expect(eval('1?0||1:2')).toEqual(B(1)?B(0)||B(1):2);
+
+        expect(eval('0?1:0&&1')).toEqual(B(0)?1:B(0)&&B(1));
+        expect(eval('0?2:1&&1')).toEqual(B(0)?2:B(1)&&B(1));
+        expect(eval('0?1:0||0')).toEqual(B(0)?1:B(0)||B(0));
+        expect(eval('0?2:0||1')).toEqual(B(0)?2:B(0)||B(1));
+
+        expect(eval('1?1:0&&1')).toEqual(B(1)?1:B(0)&&B(1));
+        expect(eval('1?2:1&&1')).toEqual(B(1)?2:B(1)&&B(1));
+        expect(eval('1?1:0||0')).toEqual(B(1)?1:B(0)||B(0));
+        expect(eval('1?2:0||1')).toEqual(B(1)?2:B(0)||B(1));
+
+        // Function calls.
+        expect(eval('returnTrue() ? returnString() : returnInt()')).toEqual(
+            returnTrue() ? returnString() : returnInt());
+        expect(eval('returnFalse() ? returnString() : returnInt()')).toEqual(
+            returnFalse() ? returnString() : returnInt());
+        expect(eval('returnTrue() ? returnString() : returnInt()')).toEqual(
+            returnTrue() ? returnString() : returnInt());
+        expect(eval('identity(returnFalse() ? returnString() : returnInt())')).toEqual(
+            identity(returnFalse() ? returnString() : returnInt()));
+      });
+
+
       it('should parse string', () {
         expect(eval("'a' + 'b c'")).toEqual("ab c");
       });