Reading integers from a text file with words

Question

I\'m trying to read just the integers from a text file structured like this....

ALS 46000
BZK 39850
CAR 38000
//....

using ifstream.

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Answer 1

Edit: it's in fact possible to work on streams directly with spirit than I suggested previously, with a parser:

+(omit[+(alpha|blank)] >> int_)

and one line of code(except for variable definitions):

void extract_file()
{
    std::ifstream f("E:/dd/dd.trunk/sandbox/text.txt");    
    boost::spirit::istream_iterator it_begin(f), it_end;

    // extract all numbers into a vector
    std::vector vi;
    parse(it_begin, it_end, +(omit[+(alpha|blank)] >> int_), vi);

    // print them to verify
    std::copy(vi.begin(), vi.end(), 
        std::ostream_iterator(std::cout, ", " ));

}

you get all numbers into a vector at once with one line, couldn't be simpler.

---

if you do not mind using boost.spirit2. the parser to get numbers from a line only is

omit[+(alpha|blank)] >> int_

to extract everything is

+(alpha|blank) >> int_

See the whole program below(Test with VC10 Beta 2):

#include   
#include   
#include   
#include  
#include   

#include 
#include 
#include 

using std::cout; 

using namespace boost::spirit;  
using namespace boost::spirit::qi;    

void extract_everything(std::string& line) 
{
    std::string::iterator it_begin = line.begin();
    std::string::iterator it_end   = line.end();    

    std::string s;
    int i;

    parse(it_begin, it_end, +(alpha|blank)>>int_, s, i);

    cout << "string " << s  
         << "followed by nubmer " << i 
         << std::endl;

}

void extract_number(std::string& line) 
{
    std::string::iterator it_begin = line.begin();
    std::string::iterator it_end   = line.end();    

    int i;

    parse(it_begin, it_end, omit[+(alpha|blank)] >> int_, i);

    cout << "number only: " << i << std::endl;

} 

void extract_line()
{
    std::ifstream f("E:/dd/dd.trunk/sandbox/text.txt");
    std::string s;
    int i; 

    // iterated file line by line
    while(getline(f, s))
    {
        cout << "parsing " << s << " yields:\n";
        extract_number(s);  // 
        extract_everything(s);
    }

}

void extract_file()
{
    std::ifstream f("E:/dd/dd.trunk/sandbox/text.txt");    
    boost::spirit::istream_iterator it_begin(f), it_end;

    // extract all numbers into a vector
    std::vector vi;
    parse(it_begin, it_end, +(omit[+(alpha|blank)] >> int_), vi);

    // print them to verify
    std::copy(vi.begin(), vi.end(), 
        std::ostream_iterator(std::cout, ", " ));

}

int main(int argc, char * argv[])  
{    
    extract_line();
    extract_file();

    return 0;  
}

outputs:

parsing ALS 46000 yields:
number only: 46000
string ALS followed by nubmer 46000
parsing BZK 39850 yields:
number only: 39850
string BZK followed by nubmer 39850
parsing CAR 38000 yields:
number only: 38000
string CAR followed by nubmer 38000
46000, 39850, 38000,