CODEWITHSUNDEEP
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Neil
Neil

Reputation: 2058

Type-out Calculator? Xcode

Not exactly sure what it would be called?

But anyway, I am wondering how exactly one would make a calculator where the user types his equation into a text box, and then when the user hits "=" it calculates everything the user has typed in.

ex. user types: 1 + 1 * (1 +2) hits enter 6 (is displayed)

-EDIT- I screwed up on my math :P 4 (is displayed)

I couldn't find any articles talking about this on the internet, for I didn't really know what to search for. So if anyone could help, or at least point me in the right direction. It would be greatly appreciated.

Thanks, Regards.

Upvotes: 0

Views: 441

Answers (4)

lnafziger
lnafziger

Reputation: 25740

These are called math parsers.

There are two very good libraries that are freely available: DDMathParser and GCMathParser.

See this question for more details.

They are much more capable than NSExpression.

Upvotes: 3

A-Live
A-Live

Reputation: 8944

1 + 1 * (1 +2) hits enter 6 (is displayed)

hmm, i'm sure there're lot of samples of human math, but 1 + 1x(1+2) != 6 :)

One recommendation from me would be to collect all unrecognized character-groups and consider it to be variables, then let a user to enter the values. Like 1 + y*(1+z), enter, y=1, z=2, enter, result=4.

Upvotes: 1

Richard J. Ross III
Richard J. Ross III

Reputation: 55573

What you are looking for is something with NSExpression I think:

NSExpression *expression = [NSExpression expressionWithFormat:inputText, nil];
NSNumber *result = [expression expressionValueWithObject:nil context:nil];

I have tested NSExpression with mathematical symbols (0-9, +, -, *, /, (, )) and it seems to work as expected. Give it a shot, it may just work for you.

Upvotes: 2

user1118321
user1118321

Reputation: 26375

You might try looking up "infix notation" and "parse trees" as a start.

Upvotes: 1

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