#304 - Parse 'if' as expression

sys27 · Oct 9, 2020 · 76af849 · 76af849
1 parent 8f33214
commit 76af849
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Showing 4 changed files with 53 additions and 37 deletions.
diff --git a/xFunc.Maths/Expressions/Programming/If.cs b/xFunc.Maths/Expressions/Programming/If.cs
@@ -63,7 +63,7 @@ public override object Execute(ExpressionParameters? parameters)
                 if (condition)
                     return Then.Execute(parameters);
 
-                return Else?.Execute(parameters) ?? 0.0;
+                return Else?.Execute(parameters) ?? new NumberValue(0.0);
             }
 
             throw new ResultIsNotSupportedException(this, result);

diff --git a/xFunc.Maths/Parser.cs b/xFunc.Maths/Parser.cs
@@ -98,7 +98,6 @@ public IExpression Parse(string function)
                ParseAssign(ref tokenReader) ??
                ParseDef(ref tokenReader) ??
                ParseUndef(ref tokenReader) ??
-               ParseIf(ref tokenReader) ??
                ParseFor(ref tokenReader) ??
                ParseWhile(ref tokenReader) ??
                ParseExpression(ref tokenReader);
@@ -165,38 +164,6 @@ public IExpression Parse(string function)
             return new Undefine(key);
         }
 
-        private IExpression? ParseIf(ref TokenReader tokenReader)
-        {
-            var @if = tokenReader.GetCurrent(IfKeyword);
-            if (@if.IsEmpty())
-                return null;
-
-            if (!tokenReader.Check(OpenParenthesisSymbol))
-                MissingOpenParenthesis(@if.Kind);
-
-            var condition = ParseConditionalOrOperator(ref tokenReader) ??
-                            throw new ParseException(Resource.IfConditionParseException);
-
-            if (!tokenReader.Check(CommaSymbol))
-                MissingComma(condition);
-
-            var then = ParseExpression(ref tokenReader) ??
-                       throw new ParseException(Resource.IfThenParseException);
-
-            IExpression? @else = null;
-            if (tokenReader.Check(CommaSymbol))
-                @else = ParseExpression(ref tokenReader) ??
-                        throw new ParseException(Resource.IfElseParseException);
-
-            if (!tokenReader.Check(CloseParenthesisSymbol))
-                MissingCloseParenthesis(@if.Kind);
-
-            if (@else is not null)
-                return new If(condition, then, @else);
-
-            return new If(condition, then);
-        }
-
         private IExpression? ParseFor(ref TokenReader tokenReader)
         {
             var @for = tokenReader.GetCurrent(ForKeyword);
@@ -288,7 +255,7 @@ public IExpression Parse(string function)
 
         private IExpression? ParseExpression(ref TokenReader tokenReader)
             => ParseBinaryAssign(ref tokenReader) ??
-               Ternary(ref tokenReader);
+               ParseTernary(ref tokenReader);
 
         private IExpression? ParseBinaryAssign(ref TokenReader tokenReader)
             => tokenReader.Scoped(this, (Parser parser, ref TokenReader reader) =>
@@ -313,7 +280,7 @@ public IExpression Parse(string function)
                 return parser.CreateBinaryAssign(@operator, variable, exp);
             });
 
-        private IExpression? Ternary(ref TokenReader tokenReader)
+        private IExpression? ParseTernary(ref TokenReader tokenReader)
             => tokenReader.Scoped(this, (Parser parser, ref TokenReader reader) =>
             {
                 var condition = parser.ParseConditionalOrOperator(ref reader);
@@ -677,12 +644,45 @@ public IExpression Parse(string function)
         private IExpression? ParseOperand(ref TokenReader tokenReader)
             => ParseComplexNumber(ref tokenReader) ??
                ParseNumber(ref tokenReader) ??
+               ParseIf(ref tokenReader) ??
                ParseFunctionOrVariable(ref tokenReader) ??
                ParseBoolean(ref tokenReader) ??
                ParseParenthesesExpression(ref tokenReader) ??
                ParseMatrix(ref tokenReader) ??
                ParseVector(ref tokenReader);
 
+        private IExpression? ParseIf(ref TokenReader tokenReader)
+        {
+            var @if = tokenReader.GetCurrent(IfKeyword);
+            if (@if.IsEmpty())
+                return null;
+
+            if (!tokenReader.Check(OpenParenthesisSymbol))
+                MissingOpenParenthesis(@if.Kind);
+
+            var condition = ParseConditionalOrOperator(ref tokenReader) ??
+                            throw new ParseException(Resource.IfConditionParseException);
+
+            if (!tokenReader.Check(CommaSymbol))
+                MissingComma(condition);
+
+            var then = ParseExpression(ref tokenReader) ??
+                       throw new ParseException(Resource.IfThenParseException);
+
+            IExpression? @else = null;
+            if (tokenReader.Check(CommaSymbol))
+                @else = ParseExpression(ref tokenReader) ??
+                        throw new ParseException(Resource.IfElseParseException);
+
+            if (!tokenReader.Check(CloseParenthesisSymbol))
+                MissingCloseParenthesis(@if.Kind);
+
+            if (@else is not null)
+                return new If(condition, then, @else);
+
+            return new If(condition, then);
+        }
+
         private IExpression? ParseParenthesesExpression(ref TokenReader tokenReader)
         {
             if (!tokenReader.Check(OpenParenthesisSymbol))

diff --git a/xFunc.Tests/Expressions/Programming/IfTest.cs b/xFunc.Tests/Expressions/Programming/IfTest.cs
@@ -70,8 +70,9 @@ public void CalculateElseTest()
 
             var cond = new Equal(Variable.X, new Number(10));
             var @if = new If(cond, new Number(20));
+            var expected = new NumberValue(0.0);
 
-            Assert.Equal(0.0, @if.Execute(parameters));
+            Assert.Equal(expected, @if.Execute(parameters));
         }
 
         [Fact]

diff --git a/xFunc.Tests/ParserTests/IfTests.cs b/xFunc.Tests/ParserTests/IfTests.cs
@@ -37,6 +37,21 @@ public void IfThenElseTest()
             ParseTest("if(x == 0 && y != 0, 2, 8)", expected);
         }
 
+        [Fact]
+        public void IfThenElseAsExpressionTest()
+        {
+            var expected = new Add(
+                Number.One,
+                new If(
+                    new Equal(Variable.X, Number.Zero),
+                    Number.Two,
+                    new Number(8)
+                )
+            );
+
+            ParseTest("1 + if(x == 0, 2, 8)", expected);
+        }
+
         [Fact]
         public void IfThenTest()
         {