copy char*

[Gary Wessle]

string a = "abcdef";
aa[80] = a.c_str();

bb[40] = how can I get def from aa in here?

thanks

[ondra.holub]

Gary Wessle napsal:

string a = "abcdef";
aa[80] = a.c_str();

bb[40] = how can I get def from aa in here?

thanks

a.c_str() + 4

But you should know, that result of c_str() method is valid only till
the first change in `a'. So you should make copy of i if you need
C-string and cannot guarantee, that no change in `a' will occure.

[SirMike]

Dnia 15 Nov 2006 22:43:39 +1100, Gary Wessle napisa³(a):

string a = "abcdef";
aa[80] = a.c_str();

bb[40] = how can I get def from aa in here?

use strncpy

--
SirMike - http://www.sirmike.org

C makes it easy to shoot yourself in the foot; C++ makes it harder, but
when you do, it blows away your whole leg. - Bjarne Stroustrup

[Default User]

Gary Wessle wrote:

>
string a = "abcdef";
aa[80] = a.c_str();

bb[40] = how can I get def from aa in here?

What are aa and bb?

Brian

[Gary Wessle]

SirMike <si*****@FUCKSP AMMERSpoczta.on et.plwrites:

Dnia 15 Nov 2006 22:43:39 +1100, Gary Wessle napisał(a):

string a = "abcdef";
aa[80] = a.c_str();

bb[40] = how can I get def from aa in here?

use strncpy

void func1(const char* p){
char frst[40];
char last[40];
strncpy(frst, p, 3); //first 3 ????
strncpy(last, p, 3); //last 3 ?????
}

string a = "abcdef";
func1(a.c_str() );

[Gary Wessle]

I want frst to have "abc" and last to have "def".

[Jim Langston]

"Gary Wessle" <ph****@yahoo.c omwrote in message
news:m3******** ****@localhost. localdomain...

SirMike <si*****@FUCKSP AMMERSpoczta.on et.plwrites:

>Dnia 15 Nov 2006 22:43:39 +1100, Gary Wessle napisal(a):

string a = "abcdef";
aa[80] = a.c_str();

bb[40] = how can I get def from aa in here?

use strncpy

void func1(const char* p){
char frst[40];
char last[40];
strncpy(frst, p, 3); //first 3 ????
strncpy(last, p, 3); //last 3 ?????
}

string a = "abcdef";
func1(a.c_str() );

void func1( const char* p )
{
char first[40];
char last[40];
strncpy( first, p, 3 );
strncpy( last, p + 3, 3 );
}

Ugly code. Prefer std::string instead.

void func1( const std::string Value )
{
std::string first = Value.substr( 0, 3 );
std::string last = Value.substr( 4, 3 );
}

[BobR]

Gary Wessle wrote in message ...

>SirMike <si*****@FUCKSP AMMERSpoczta.on et.plwrites:

>use strncpy

void func1(const char* p){
char frst[40];
char last[40];
strncpy(frst, p, 3); //first 3 ????
strncpy(last, p, 3); //last 3 ?????
}

string a = "abcdef";
func1(a.c_str( ));

void func1( char const *p, std::ostream &out ){
char frst[ 40 ];
char last[ 40 ];
strncpy( frst, p, 3 ); //first 3 ????
strncpy( last, p+3, 3 ); //last 3 ?????
out << "frst="<<frst<< " last="<<last<<s td::endl;
return;
}

{
std::string a = "abcdef";
func1( a.c_str(), std::cout );
}
// out: frst=abc last=def

--
Bob R
POVrookie

[Default User]

BobR wrote:

void func1( char const *p, std::ostream &out ){
char frst[ 40 ];
char last[ 40 ];
strncpy( frst, p, 3 ); //first 3 ????
strncpy( last, p+3, 3 ); //last 3 ?????
out << "frst="<<frst<< " last="<<last<<s td::endl;
return;
}

{
std::string a = "abcdef";
func1( a.c_str(), std::cout );
}
// out: frst=abc last=def

Did you actually try this? If you got the purported results, then it
was by sheer bad luck. You didn't terminate the string, and strncpy
doesn't do it for you. Outputting the result was undefined behavior.


Brian

[Gary Wessle]

#include <string>
#include <iostream>
using namespace std;

class myType {
protected:
char _frst[40];
char _second[40];
char _pair[80];
public:
const char* frst() const;
const char* second() const;
myType(const char* pair);
};

myType::myType( const char* pair)
{
strncpy(_frst, pair, 3);
strncpy(_second , pair+4, 3);
}
const char* myType::frst()c onst {return _frst;}
const char* myType::second( )const {return _second;}

int main(){
string s = "abc-def";
myType mt(s.c_str());
string tmp = mt.frst();
string tmp2 = mt.second();
cout << tmp << " " << tmp2 << endl;
}

//output
abcMh Q%G.ANoN?N =NoN?N=NoN ?N=NoN?N=% @`%G.ANoN? N=%@M$B'\(B $B%G.ANoN? N=(B$B%@(B def