shunting-yard

A mathematical expression is usually expressed in infix notation. For evaluation purposes, we can change it to postfix (reverse polish) notation (using algorithms like Shunting-Yard ) and then evaluate the postfix notation using stack. I found out that calculators use this technique, but do today's modern compilers use this for arithmetic expression evaluation? Is it efficient enough or other techniques (or algorithms) are being used? To answer this question let's focus on the concepts you mention, infix notation , Shunting-Yard and evaluation and then relate them to compiling. To start with

I'm currently trying to parse math expression into expression tree. But I'm stuck on the stage where I need to implement functions and negates. I don't understand logic to do it using Shunting-Yard algorithm. What I currently want to do is to support Negates, like -(x+5) Function calls, like min(x,y) Power just after function name, like cos^2(x) Implicit multiplication, like 2x is same as 2*x Scientific notation Constants e and pi Can somebody tell me hints how to implement this? An working , PSR-0 compatible implementation of the shunting yard algorithm can be found here: https://github.com

The I/p to the algo will be an expression like this: a+(-b) a*-b+c i.e any expression that a standard C compiler would support. Now I've the input already formatted as a stream of tokens , the tokens contain info whether its an operator or an operand. The algorithm should take this in and give me a postfix expression that I can evaluate. If I use the standard conversion algo, I cant differentiate between an unary and a binary op . Like a*(-b) would give me ab-* ,which would evaluate in the wrong way. If an operator is the first thing in your expression, or comes after another operator, or

I've been looking at the wiki page: http://en.wikipedia.org/wiki/Shunting-yard_algorithm I've used the code example to build the first part, basically I can currently turn : 3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3 into 3 4 2 * 1 5 − 2 3 ^ ^ / + But I don't know how to then use 3 4 2 * 1 5 − 2 3 ^ ^ / + to obtain 3.00012207 And the example code and explanation on wiki aren't making any sense to me. Could someone please explain how to evaluate 3 4 2 * 1 5 − 2 3 ^ ^ / + and produce the answer. Thanks in advance. I don't need a code example just a good explanation or a breakdown of an example. Not that it

Is there a better way to handle unary "-" in converting a infix expression to a postfix one? The obvious one would be prefix every unary "-" with a 0. Does anyone know better implementation? Thanks! The way I did this years ago was invent a new operator for my postfix expression. So when I encountered a unary minus in the infix, I'd convert it to # . So my postfix for a + -b became ab#+ . And, of course, my evaluator had to know that # only popped one operand. Kind of depends on how you're using the postfix expression once it's built. If you want to display it then your special # operator

I've been working on implementing the Shunting-Yard Algorithm in JavaScript for class. Here is my work so far: var userInput = prompt("Enter in a mathematical expression:"); var postFix = InfixToPostfix(userInput); var result = EvaluateExpression(postFix); document.write("Infix: " + userInput + "<br/>"); document.write("Postfix (RPN): " + postFix + "<br/>"); document.write("Result: " + result + "<br/>"); function EvaluateExpression(expression) { var tokens = expression.split(/([0-9]+|[*+-\/()])/); var evalStack = []; while (tokens.length != 0) { var currentToken = tokens.shift(); if (isNumber

I'm looking for something that can interpret a string in php and perform simple math calculation, and then return a boolean result as to whether the expression is true or false. For example: Sue types in "3*{mysalary}/9=10000" PHP splits this up into two expressions - explode('=',string); PHP takes my list of database fields, and replaces any "{}" delimited fields with the data (typecasted to int) PHP then evaluates the maths expression php then compares the left side to the right side boolean result produced. It may sound complex but it only needs to be very simple. Here are the constraints: