Created
September 13, 2020 08:32
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Calculator Evaluator
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| // Evalutor.cs | |
| public class Evaluator | |
| { | |
| public static Object.Object Eval(Expression expression) | |
| { | |
| if(expression is AST.IntegerExpression) | |
| { | |
| return new Object.IntegerObject { Value = ((IntegerExpression)expression).Value }; | |
| } | |
| if(expression is AST.PrefixExpression) | |
| { | |
| return EvalPrefixExpression(expression as AST.PrefixExpression); | |
| } | |
| if(expression is AST.InfixExpression) | |
| { | |
| return EvalInfixExpression(expression as AST.InfixExpression); | |
| } | |
| throw new Exception($"Unsupported expression {expression.TokenLiteral()}"); | |
| } | |
| public static Object.Object EvalPrefixExpression(AST.PrefixExpression expression) | |
| { | |
| Object.Object right = Eval(expression.Right); | |
| Object.IntegerObject rightInteger = right as Object.IntegerObject; | |
| if(rightInteger == null) | |
| { | |
| throw new Exception("Prefix expression right is not Object.IntegerObject"); | |
| } | |
| return new Object.IntegerObject { Value = -1 * rightInteger.Value }; | |
| } | |
| public static Object.Object EvalInfixExpression(AST.InfixExpression expression) | |
| { | |
| Object.Object left = Eval(expression.Left); | |
| Object.IntegerObject leftInteger = left as Object.IntegerObject; | |
| if(leftInteger == null) | |
| { | |
| throw new Exception("Infix expression left branch is not Object.IntegerObject"); | |
| } | |
| Object.Object right = Eval(expression.Right); | |
| Object.IntegerObject rightInteger = right as Object.IntegerObject; | |
| if(rightInteger == null) | |
| { | |
| throw new Exception("Infix expression right branch is not Object.IntegerObject"); | |
| } | |
| return InfixExpression(leftInteger, expression.Operator, rightInteger); | |
| } | |
| public static Object.Object InfixExpression(Object.IntegerObject left, string op, Object.IntegerObject right) | |
| { | |
| if(op == "+") | |
| { | |
| return new Object.IntegerObject { Value = left.Value + right.Value }; | |
| } | |
| if(op == "-") | |
| { | |
| return new Object.IntegerObject { Value = left.Value - right.Value }; | |
| } | |
| if(op == "*") | |
| { | |
| return new Object.IntegerObject { Value = left.Value * right.Value }; | |
| } | |
| if(op == "/") | |
| { | |
| return new Object.IntegerObject { Value = left.Value / right.Value }; | |
| } | |
| if(op == "^") | |
| { | |
| return new Object.IntegerObject { Value = (long)Math.Pow((double)left.Value, (double)right.Value) }; | |
| } | |
| throw new Exception($"Unsupported arithmetic operator {op}"); | |
| } | |
| } |
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