C#, How to compute an operation string

Question

i have a string like that

str = "4975 + 10 * (LOG(250.6)) - 321.2"

i want to compute the result of this operation. Is there any sort way to do that?

// my operation just includes some of operators (,), +, -, *, / , ., 0-9, LOG
// '.' is used for double number

@Rob I do not think that is the short way the OP is thinking of :) — Brian Ogden, May 07 '17 at 03:59
No there is no short way to do this, you have to parse the string or present a user interface that allows someone to type numbers and press a log, substract, add button, aka a calculator interface than you do not have to parse a string at all — Brian Ogden, May 07 '17 at 04:00
You can check this post http://stackoverflow.com/questions/333737/evaluating-string-342-yield-int-18 — hardkoded, May 07 '17 at 04:10
Hmm, that duplicate is outdated and also closed, as a dupe of a question that asks specifically for _compilation_. I think this deserves a fresh start. Reopening. — H H, May 07 '17 at 04:36
@HenkHolterman I dunno, answers for this question will be people either suggesting their favorite lexing/parsing libraries or suggesting that OP write his own. Either way, I'd agree with the question getting closed. — Abion47, May 07 '17 at 05:11

score 7 · Accepted Answer · answered May 07 '17 at 04:18

I believe this is what you are looking for.

Use this library will help you to perform math operations in string format

Add this package

Install-Package DynamicExpresso.Core

code example

public static void Main(string[] args)
        {
            var interpreter = new Interpreter();
            var result = interpreter.Eval("4975 + 10 * (LOG(250.6)) - 321.2".Replace("LOG", "Math.Log"));

            Console.WriteLine("result=> " + result);
            Console.ReadKey();
        }

result=> 4709.03858042462

link for lib https://github.com/davideicardi/DynamicExpresso

Thank you. It's really helpful. I even found a feature (working with variables and parameters) that i really need. — Trương Anh, May 08 '17 at 13:04

score 1 · Answer 2 · edited May 23 '17 at 12:10

1

Also answered here:

https://stackoverflow.com/a/2859130/1043824

Try DataTable.Compute

I do not have a .net box lying around so I cannot confirm whether it can do log or not, but I have used it for long algebric expressions.

Basically this is how it goes:

DataTable dt = new DataTable();
var ans = dt.compute("5 + (7 - 9) / 3");

edited May 23 '17 at 12:10

Community

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answered May 07 '17 at 04:26

inquisitive

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Yes, but DataTable is limited and unavailable in dotnet core. – H H May 07 '17 at 04:37
It works well with double number and "+ - * /" operator. But It doesn't work with Log. I get it a exception like this: Unhandled Exception: System.Data.EvaluateException: The expression contains undefined function call Log(). – Trương Anh May 08 '17 at 12:19

C#, How to compute an operation string

2 Answers2