Translate string into int type.

[bolo809]

Hi Guys,
I want translate a number string into int type. such as "21354" to (int)21354. but the output is not correct. I can not find bugs. Please help me. Thanks.

#include <iostream>

using namespace std;


int main(){
	char tm[20] = "2135";
		
	const char tran = '0';
	
	int tmp=0;
	
	for(int tm_i=0;tm_i<20;tm_i++){
		if(tm[tm_i]=='\0')tmp=tm_i;
	}
		
	
	int intnum = 0;
	for(int i=tmp, int j=1,int flag=0;i>=0;i--){
		if(flag == 1){
			intnum += (int)(tm[i] - tran)*j;
			j*=10;
		}
		if(tm[i]=='\0')flag=1;
	}
	
	cout<<"string is:"<<tm<<endl;
	cout<<"int number is:"<<intnum<<endl;
	
	
	return 0;
}

string is:2135
int number is:-995611984

[arrias]

The atoi() method does this for you.

#include <cstdlib>
int atoi(const char *str);

[blackcoder41]

http://cplusplus.com/articles/numb_to_text/

int str2int (const string &str) {
  stringstream ss(str);
  int n;
  ss >> n;
  return n;
}

string int2str (int n) {
  stringstream ss;
  ss << n;
  return ss.str();
}

[bolo809]

@arrias: Thanks, I found it in http://www.cplusplus.com/reference/clibrary/cstdlib/atoi/.

[blackcoder41]

nice.. but i hope you know its non-standard..

[Duthomhas]

What do you mean it is non-standard?

It is in the C Standard Library. It is standard according to SVr4, POSIX.1-2001, 4.3BSD, C99, C89 and POSIX.1-1996. http://linux.die.net/man/3/atoi


It is not, however, C++. If you plan to use C++, then use C++ and avoid old stuff like atoi(). blackcoder41 has done you a double service already by both posting nice, drop-in code you can use and linking to a very well-written article which exactly answers your topic question.

[blackcoder41]

sorry, i mean it's not ANSI C

[Duthomhas]

YES IT IS.

I already wrote:

It is standard according to ... C89 [AKA ANSI C] ... http://linux.die.net/man/3/atoi

Maybe you are thinking of itoa(), which is common (but non-standard)?

[blackcoder41]

oh yes it's itoa(), my mistake. just forget it.. thanks for correcting me anyway..

i'll just have your word.

which is common (but non-standard)

[Duthomhas]

I only know because when I first began coding I used atoi() and itoa(), and was both surprised and peeved that the latter was so, well, non-portable (making code I wrote at home not work at school). Then I learned about such things as standards...