How to make condition for specific template datatypes

Question

so i made a very simple stack that works just fine and decided to turn it to template, it also worked fine, but when i turned it to integer something happened with the input

string m;
    getline(cin, m);
    linkedliststack<int> str;
    for (int i = 0; i < m.length(); i++)
    {
        str.push(m[i]);
    }

It appeared that by using this input method the m[i] becomes char turned to int, in other words turned to ASCII code, so if i enter 1 it give 48, 2 give 49 etc. The simple solution is of course this.

str.push(m[i]-48)

But is there a way to make it automated, e.i. with if condition or anything? If yes then what is the required syntax?

Thanks.

You're not looking for data type conversion, you're looking for parsing a string into a numeric value. — SirGuy, Jul 28 '16 at 21:33
Possibly look into using stoi Reference: http://www.cplusplus.com/reference/string/stoi/ — Omid CompSCI, Jul 28 '16 at 21:36
The problem is easy to solve i just want it to be automated, e.g. detect that the template is now and then activates 'str.push(m[i]-48)' by itself — AHAMES, Jul 28 '16 at 21:50

score 0 · Answer 1 · answered Jul 28 '16 at 21:38

0

Strings push_back is

void push_back (char c);

i.e. it takes a char. If you want the value as a char you have to convert it by using e.g. itoa or the like.

answered Jul 28 '16 at 21:38

463035818_is_not_an_ai

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score 0 · Answer 2 · edited May 23 '17 at 11:59

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I must apologize for repeating this question as it is related to this on How do I get the type of a variable? sorry this is my first time to ask a question.

So to solve this i made a new function in the class

string type(){ return  typeid(head->value).name(); }

and the new condition solves the problem.

if (str.type()== "int")

edited May 23 '17 at 11:59

Community

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answered Jul 28 '16 at 22:36

AHAMES

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Tomas Dittmann · Answer 3 · 2016-07-28T23:16:52.970

There may be an enable_if solution out there if you're able to use C++14. Maybe even an SFINAE solution. However I'm not very experienced with that.

I'm assuming your push method is declared as

void push(typename T);

Then what you are doing is implicitly converting a char (m[i]) to an int str.push(m[i]);

You could provide an overloaded template method that can handle a char Input and convert it correctly to your typename.

Something like this:

void push(const char input)
{
    push(atoi(input));
    // push(input-48);
}

A lot of errors may have to be considered though: What happens if atoi() cannot convert the char to an integer? In your case of -48 you will push unintended numbers on the Stack if input is a nonnumber char. What will happen if the template is not instantiated with .

How to make condition for specific template datatypes

3 Answers3