Arduino | String to Int Math Expression

Question

I have string math expression. I want to convert this expression to integer.

Example:

    char str[]="2*5";

So, I need to get 10 for this example in arduino. How can I do that ?

This is very close to your question and should help you to find the solution of refine the question https://stackoverflow.com/questions/9329406/evaluating-arithmetic-expressions-from-string-in-c — Julien, Apr 16 '18 at 08:13

score 1 · Accepted Answer · answered Apr 16 '18 at 00:36

a naive solution would be to split the expression (using regex or even sscanf [even though i do not recommend it] ) to numbers (cast the numbers to int\doubles of course) and operator(that could stay as a string ) and switch case the math operator action with the numbers (as in activating the relevant operator).

a better solution in my opinion is to use SY algorithem (wiki) to convert the expression to a Reverse Polish notation(wiki) which makes things much easier to parse and work with (especially if youll use a stack to parse it )

also found some useful answers here(evaluating from string), here (split string with math expression) and my personal favorite here (evaluate arithmetic from string)

score 1 · Answer 2 · answered Apr 18 '18 at 16:33

1

I did it with TinyExpr library. It worked like a charm !

https://github.com/codeplea/tinyexpr/blob/master/README.md

answered Apr 18 '18 at 16:33

Furkan Salık

23
4

Excellent advice, and excellent library. Thanks! – Eric Duminil May 06 '21 at 17:48

score -1 · Answer 3 · answered Apr 15 '18 at 16:43

-1

You can't do this in quotation marks. Maybe you want just parse it to String:

int x = 2*5
String myString = String(x);

answered Apr 15 '18 at 16:43

kacmak7

131
2
9

But I'm getting expression in string type. So I need parse string to int. – Furkan Salık Apr 15 '18 at 17:09
Then, use ' toInt() ' function on string object, but you can't do math in string. – kacmak7 Apr 15 '18 at 19:07
1

"2*5" returns 2. – Furkan Salık Apr 15 '18 at 20:33

Arduino | String to Int Math Expression

3 Answers3