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string to int

Started by Craazer 14 replies 1.9k views
Original Post
Craazer
Craazer
Hi! This is probably often asked queston but the search engine doesn''t work right now... So how can I convert string to int or double? Converting backwards isn''t a problem becose I use wsprintf() for that, or is it a good solution?
Jolle
Jolle
int atoi(char*)
SabreMan
SabreMan
quote:
Original post by Craazer
Hi! This is probably often asked queston but the search engine doesn''t work right now...

You could have fooled me!
quote:

So how can I convert string to int or double?

You could try using the `parse-integer'' function.
dalleboy
dalleboy
quote:
Original post by SabreMan
You could try using the `parse-integer'' function.

I don''t think he was asking about the lisp function as he said that he was using wsprintf to convert from int to string...


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dalleboy
dalleboy
quote:
Original post by Craazer
So how can I convert string to int or double?

You have a lot of options here: The atoi function, the boost::lexical_cast operator, the stringstream class are only three of them.
quote:
Converting backwards isn''t a problem becose I use wsprintf() for that, or is it a good solution?

wsprintf is Windows only, sprintf (or snprintf) is more portable. There are a lot of options for you here as well: the boost::lexical_cast operator, the stringstream class are only a few of them.


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Qw3r7yU10p!
Qw3r7yU10p!
string to integer works similarly, by the way
civguy
civguy
quote:
Original post by Craazer
Hi! This is probably often asked queston but the search engine doesn''t work right now...
Google does. ''"string to int" c'' gave immediately results. If people only did at least the minimum amount of searching before asking... maybe Gamedev forums wouldn''t exist then though.
Craazer
Craazer
quote:
Original post by civguy
[quote]Original post by Craazer
Hi! This is probably often asked queston but the search engine doesn''t work right now...
Google does. ''"string to int" c'' gave immediately results. If people only did at least the minimum amount of searching before asking... maybe Gamedev forums wouldn''t exist then though.

Probably would''t and the bad thing when searhing whit google is that strings and ints are in many langueges like java (what was the first search result).

However it seems that stringstream class is a good solution...
So great I can use that then, but when posting this thread I was hoping to learn about the actual technique as practice.

And when I said string I actualy ment string types and char arrays or pointers as strings, but I gues you can copy char arrays to string types.


davepermen
davepermen
just.. do it yourself..

read the first char. is it a number, get the number out of it. read next char, if its a number, multiply current value by 10, add new number to it, etc..


  
bool isDigit(char chr) { return chr >= ''0'' && chr <= ''9''; }

char* chr = beginning_of_string;
while(*chr) { if(isDigit(chr)) break; ++chr; }
int number = 0;
do {
  number *= 10;
  number += *chr - ''0'';
  chr++;
}while(*chr && isDigit(chr));


something like this. i''m very very very tierd..:D

"take a look around" - limp bizkit
www.google.com
If that's not the help you're after then you're going to have to explain the problem better than what you have. - joanusdmentia
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Craazer
Craazer
quote:
Original post by davepermen
just.. do it yourself..

read the first char. is it a number, get the number out of it. read next char, if its a number, multiply current value by 10, add new number to it, etc..


    
bool isDigit(char chr) { return chr >= ''0'' && chr <= ''9''; }

char* chr = beginning_of_string;
while(*chr) { if(isDigit(chr)) break; ++chr; }
int number = 0;
do {
  number *= 10;
  number += *chr - ''0'';
  chr++;
}while(*chr && isDigit(chr));


something like this. i''m very very very tierd..:D

"take a look around" - limp bizkit
www.google.com

Thanks, actualy I just ended trying to do shometing similar becose the dot was kinda difficult to handle becose my solution took lot of speed. Well will be trying again later becose im very very tired too

civguy
civguy
quote:
Original post by Craazer
Probably would''t and the bad thing when searhing whit google is that strings and ints are in many langueges like java (what was the first search result).
That''s why you add ''C'' or ''C++'' to the search string.

billybob
billybob
the inverse of sprintf is sscanf
Illumini
Illumini
itoa()
atoi()

other handy things ltoa(), atol(), etc

funny thing tho.. ftoa is missing, there is a atof tho.

itoa/ltoa do take a few extra things... a buffer to put string in... then the number, then a radix, usualy 10 (10 base number system is what we humans like to count in anyway
SabreMan
SabreMan
quote:
Original post by Illumini
itoa()
atoi()

Those functions are not recommended. atoi() yields undefined behaviour when the input cannot be converted, and itoa() isn''t a C function.
Qw3r7yU10p!
Qw3r7yU10p!
just looking at ''Thinking in C++'' and found this code example:


  
//: C03:stringConv.h

// Chuck Allison''s string converter

#ifndef STRINGCONV_H
#define STRINGCONV_H
#include <string>
#include <sstream>
template<typename T>
T fromString(const std::string& s) {
    std::istringstream is(s);
    T t;
    is >> t;
    return t;
}
template<typename T>
    std::string toString(const T& t) {
    std::ostringstream s;
    s << t;
    return s.str();
}
#endif // STRINGCONV_H ///:~


quote:

Here’s a test program, that includes the use of the Standard Library complex number type:


  //: C03:stringConvTest.cpp

#include "stringConv.h"
#include <iostream>
#include <complex>
using namespace std;
int main() {
    int i = 1234;
    cout << "i == \"" << toString(i) << "\"\n";
    float x = 567.89;
    cout << "x == \"" << toString(x) << "\"\n";
    complex<float> c(1.0, 2.0);
    cout << "c == \"" << toString(c) << "\"\n";
    cout << endl;
    i = fromString<int>(string("1234"));
    cout << "i == " << i << endl;
    x = fromString<float>(string("567.89"));
    cout << "x == " << x << endl;
    c = fromString< complex<float> >(string("(1.0,2.0)"));
    cout << "c == " << c << endl;
} ///:~


quote:

The output is what you’d expect:
i == "1234"
x == "567.89"
c == "(1,2)"
i == 1234
x == 567.89
c == (1,2)

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