How to calculate string fields as double.

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3.00/5 (2 votes)

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I have

C++

String res="120*10-50%5";

The answer is 230.

How can I parse this as double?
How can I calculate this?

Please help me.

Posted 19-Nov-11 23:05pm

thanga__raj

Updated 20-Nov-11 20:03pm

TorstenH.

v3

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André Kraak 20-Nov-11 5:07am

Edited question:
Added pre tags

Sergey Alexandrovich Kryukov 20-Nov-11 19:04pm

I really wonder "why". For compiled question it's not so easy and lead for such a big fields as "Computer Algebra Systems (CAS)". (And yes, it's quite possible to develop one using Java). Just arithmetic evaluation is a highly simplified case of such thing. Again, why going into it? I would say, development of CAS is very difficult but would make sense, but just arithmetic expression evaluation -- hardly. Can you justify such work?
--SA

TorstenH. 21-Nov-11 2:03am

did anyone figure out the pure failure of this calculation?

(120*10)-(50%5) = 1190

The rest of the homework should be done by the questioner. I added tags for that

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DaveAuld · Answer 1 · 2011-11-19T23:36:00

Solution 1

What you are looking for is Arithmetic Evaluation functions.

See this question and answers over at SO; http://stackoverflow.com/questions/4173623/mathematical-expression-string-to-number-in-java[^]

There are various articles for this and also libraries you could use if you just search around.

Posted 19-Nov-11 23:36pm

DaveAuld

Comments

RaviRanjanKr 21-Nov-11 2:13am

My 5+

**JF2015** · Answer 2 · 2011-11-20T20:09:00

Solution 2

Have a look at this great CodeProject article:
Evaluating Mathematical Expressions by Compiling C# Code at Runtime[^]
or this library:
Parsing Mathematical Expressions with muParser[^]
http://muparser.sourceforge.net/[^]

Posted 20-Nov-11 20:09pm

JF2015

Comments

RaviRanjanKr 21-Nov-11 2:13am

My 5+