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# string to int

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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?

int atoi(char*)

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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.

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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...

Update GameDev.net system time campaign - success at last

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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.

Update GameDev.net system time campaign - success at last

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string to integer works similarly, by the way

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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.

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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.

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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

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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

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

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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.

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the inverse of sprintf is sscanf

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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

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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.

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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)