#119 - Add support of ternary operator

xFunc Grammar.txt

@@ -6,6 +6,7 @@ statement = unaryAssign
           / def
           / undef
           / if
+          / ternary
           / for
           / while
           / exp
@@ -19,6 +20,7 @@ def = ('def' / 'define') '(' assignmentKey ',' exp ')'
 undef = ('undef' / 'undefine') '(' assignmentKey ')'
 
 if = 'if' '(' conditional ',' exp (',' exp)* ')'
+ternary = conditional '?' exp ':' exp
 for = 'for' '(' statement ',' exp ',' conditional ',' statement ')'
 while = 'while' '(' exp ',' conditional ')'
 

xFunc.Maths/Parser.ExpressionFactory.cs

@@ -291,5 +291,8 @@ private IExpression CreateUnaryMinus(IExpression operand)
 
         private IExpression CreateMultiplication(params IExpression[] arguments)
             => new Mul(arguments);
+
+        private IExpression CreateTernary(IExpression condition, IExpression then, IExpression @else)
+            => new If(condition, then, @else);
     }
 }

xFunc.Maths/Parser.cs

@@ -80,6 +80,7 @@ private IExpression Statement(TokenReader tokenReader)
                    Def(tokenReader) ??
                    Undef(tokenReader) ??
                    If(tokenReader) ??
+                   Ternary(tokenReader) ??
                    For(tokenReader) ??
                    While(tokenReader) ??
                    Expression(tokenReader);
@@ -246,6 +247,39 @@ private IExpression If(TokenReader tokenReader)
             return CreateFromKeyword(@if, condition, then);
         }
 
+        private IExpression Ternary(TokenReader tokenReader)
+        {
+            var scope = tokenReader.CreateScope();
+
+            var condition = ConditionalOperator(tokenReader);
+            if (condition == null)
+            {
+                tokenReader.Rollback(scope);
+
+                return null;
+            }
+
+            if (!tokenReader.Symbol(SymbolToken.QuestionMark))
+            {
+                tokenReader.Rollback(scope);
+
+                return null;
+            }
+
+            var then = Expression(tokenReader) ??
+                       throw new ParseException(Resource.TernaryThenParseException);
+
+            if (!tokenReader.Symbol(SymbolToken.Colon))
+                throw new ParseException(Resource.TernaryColonParseException);
+
+            var @else = Expression(tokenReader) ??
+                        throw new ParseException(Resource.TernaryElseParseException);
+
+            tokenReader.Commit();
+
+            return CreateTernary(condition, then, @else);
+        }
+
         private IExpression For(TokenReader tokenReader)
         {
             var @for = tokenReader.Keyword(KeywordToken.For);

xFunc.Maths/Resources/Resource.resx

@@ -196,4 +196,13 @@
   <data name="ValueIsNotInteger" xml:space="preserve">
     <value>The value is not an integer.</value>
   </data>
+  <data name="TernaryThenParseException" xml:space="preserve">
+    <value>Cannot parse 'then' statement of ternary operator.</value>
+  </data>
+  <data name="TernaryElseParseException" xml:space="preserve">
+    <value>Cannot parse 'else' statement of ternary operator.</value>
+  </data>
+  <data name="TernaryColonParseException" xml:space="preserve">
+    <value>The ':' symbol is expected 'then' expression.</value>
+  </data>
 </root>

xFunc.Maths/Resources/Resource.ru.resx

@@ -196,4 +196,13 @@
   <data name="ValueIsNotInteger" xml:space="preserve">
     <value>Значение не является целым числом.</value>
   </data>
+  <data name="TernaryElseParseException" xml:space="preserve">
+    <value>'else' в тернарном операторе не может быть распарсено.</value>
+  </data>
+  <data name="TernaryThenParseException" xml:space="preserve">
+    <value>'then' в тернарном операторе не может быть распарсено.</value>
+  </data>
+  <data name="TernaryColonParseException" xml:space="preserve">
+    <value>Ожидается символ ':' после выражения 'then'.</value>
+  </data>
 </root>

xFunc.Maths/Tokenization/Lexer.OperatorToken.cs

@@ -28,8 +28,8 @@ private IToken CreateOperatorToken(ref ReadOnlyMemory<char> function)
         {
             var span = function.Span;
             var first = span[0];
-            var second = span.Length >= 2 ? (char?)span[1] : null;
-            var third = span.Length >= 3 ? (char?)span[2] : null;
+            var second = span.Length >= 2 ? span[1] : default;
+            var third = span.Length >= 3 ? span[2] : default;
 
             var (token, size) = (first, second, third) switch
             {

xFunc.Maths/Tokenization/Lexer.cs

@@ -46,10 +46,10 @@ public IEnumerable<IToken> Tokenize(string function)
             while (memory.Length > 0)
             {
                 var result = SkipWhiteSpaces(ref memory) ??
-                             CreateSymbol(ref memory) ??
                              CreateNumberToken(ref memory) ??
                              CreateIdToken(ref memory) ??
-                             CreateOperatorToken(ref memory);
+                             CreateOperatorToken(ref memory) ??
+                             CreateSymbol(ref memory);
 
                 if (result == null)
                     throw new TokenizeException(string.Format(CultureInfo.InvariantCulture, Resource.NotSupportedSymbol, memory.Span[0]));
@@ -83,6 +83,8 @@ private IToken CreateSymbol(ref ReadOnlyMemory<char> function)
                 ',' => Comma,
                 '∠' => Angle,
                 '°' => Degree,
+                ':' => Colon,
+                '?' => QuestionMark,
                 _ => null,
             };
 

xFunc.Maths/Tokenization/Tokens/SymbolToken.cs

@@ -71,5 +71,15 @@ private SymbolToken(char symbol)
         /// Gets the '°' token.
         /// </summary>
         public static SymbolToken Degree { get; } = new SymbolToken('°');
+
+        /// <summary>
+        /// Gets the ':' token.
+        /// </summary>
+        public static SymbolToken Colon { get; } = new SymbolToken(':');
+
+        /// <summary>
+        /// Gets the '?' token.
+        /// </summary>
+        public static SymbolToken QuestionMark { get; } = new SymbolToken('?');
     }
 }

xFunc.Maths/Tokenization/TokensBuilder.cs

@@ -205,6 +205,24 @@ public TokensBuilder Degree()
             return Symbol(SymbolToken.Degree);
         }
 
+        /// <summary>
+        /// Adds colon symbol token.
+        /// </summary>
+        /// <returns>The current instance of builder.</returns>
+        public TokensBuilder Colon()
+        {
+            return Symbol(SymbolToken.Colon);
+        }
+
+        /// <summary>
+        /// Adds question mark symbol token.
+        /// </summary>
+        /// <returns>The current instance of builder.</returns>
+        public TokensBuilder QuestionMark()
+        {
+            return Symbol(SymbolToken.QuestionMark);
+        }
+
         /// <summary>
         /// Adds variable token.
         /// </summary>

xFunc.Tests/ParserTests/IfTests.cs

@@ -14,6 +14,7 @@
 // limitations under the License.
 
 using xFunc.Maths.Expressions;
+using xFunc.Maths.Expressions.LogicalAndBitwise;
 using xFunc.Maths.Expressions.Programming;
 using xFunc.Maths.Tokenization.Tokens;
 using Xunit;
@@ -204,5 +205,65 @@ public void IfMissingClose()
 
             ParseErrorTest(tokens);
         }
+
+        [Fact]
+        public void TernaryTest()
+        {
+            var tokens = Builder()
+                .True()
+                .QuestionMark()
+                .Number(1)
+                .Colon()
+                .Operation(OperatorToken.Minus)
+                .Number(1)
+                .Tokens;
+
+            var exp = parser.Parse(tokens);
+            var expected = new If(
+                new Bool(true),
+                new Number(1),
+                new UnaryMinus(new Number(1)));
+
+            Assert.Equal(expected, exp);
+        }
+
+        [Fact]
+        public void TernaryElseMissingTest()
+        {
+            var tokens = Builder()
+                .True()
+                .QuestionMark()
+                .Number(1)
+                .Colon()
+                .Tokens;
+
+            ParseErrorTest(tokens);
+        }
+
+        [Fact]
+        public void TernaryIfMissingTest()
+        {
+            var tokens = Builder()
+                .True()
+                .QuestionMark()
+                .Colon()
+                .Operation(OperatorToken.Minus)
+                .Number(1)
+                .Tokens;
+
+            ParseErrorTest(tokens);
+        }
+
+        [Fact]
+        public void TernaryColonMissingTest()
+        {
+            var tokens = Builder()
+                .True()
+                .QuestionMark()
+                .Number(1)
+                .Tokens;
+
+            ParseErrorTest(tokens);
+        }
     }
 }

xFunc.Tests/Tokenization/LexerTest.cs

@@ -1412,6 +1412,22 @@ public void IfElseNegativeTest()
             Assert.Equal(expected, tokens.ToList());
         }
 
+        [Fact]
+        public void TernaryOperatorTest()
+        {
+            var tokens = lexer.Tokenize("True ? 1 : -1");
+            var expected = Builder()
+                .True()
+                .QuestionMark()
+                .Number(1)
+                .Colon()
+                .Operation(OperatorToken.Minus)
+                .Number(1)
+                .Tokens;
+
+            Assert.Equal(expected, tokens.ToList());
+        }
+
         [Fact]
         public void ForTest()
         {