functions and email

[laura fidarova]

Q: highlight (or determine)the email address from the string using function.

ex: input(from the console) : hgg gcgchj jkvvhc [e-mail] igvjbkn gvjkh
output: [e-mail]

i'm guessing i need to use regex here? could you please explain how to properly do it?

i started something but i guess it's pointless

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

double it_is_email(double string, double email) {

	const regex pattern
	("(\\w+)(\\.|_)?(\\w*)@(\\w+)(\\.(\\w+))+");

[Handy Andy]

Hello laura fidarova,

I do not know much about regex, but you may find this helpful.

https://regex101.com/r/yR2jyH/1

Andy

[JLBorges]

A regular expression that matches as per RFC 5322 would be horrendously complex.
Here is a simplified version that would match most real-life email addresses.

#include <iostream>
#include <string>
#include <regex>

std::string get_email_address( const std::string& str )
{
    // somewhat simplified regex for email address (does not handle al edge cases)
    // valid characters in the address (anything other than @, space, tab, line feed, new line)
    static const std::string valid_char = "[^@ \\t\\r\\n]" ;
    static const std::string vcs = valid_char + '+' ; // sequence of one or more valid chars

    // simple email address of the form [e-mail] 
    static const std::regex email_addr_re( vcs + '@' + vcs + "\\." + vcs );

    std::smatch match ;
    // if a match for an email address pattern is found, return the found address
    if( std::regex_search( str, match, email_addr_re ) ) return match[0] ;
    else return {} ; // no match, return an empty string
}

// simple test driver
int main()
{
    const std::string test_str = "hgg gcgchj jkvvhc [e-mail] igvjbkn gvjkh" ;
    const std::string email = get_email_address( test_str ) ;
    if( !email.empty() ) std::cout << "found email address '" << email << "'\n" ;
}

http://coliru.stacked-crooked.com/a/63f85c4cbe70857e

[againtry]

#include <iostream>
#include <string>

using namespace std;

int main()
{
    std::string blather{"hgg gcgchj jkvvhc [e-mail] igvjbkn gvjkh"};
    
    size_t at_position = blather.find('@');
    size_t left_position{0};
    size_t right_position{0};
    
    size_t ndx{at_position};
    while(ndx >= 0 && blather[ndx] != ' ')
    {
        ndx--;
    }
    left_position = ndx + 1;
    
    ndx = at_position;
    while(ndx < blather.length() && blather[ndx] != ' ')
    {
        ndx++;
    }
    right_position = ndx;
    
    std::string email_address = blather.substr(left_position, right_position - left_position);
    std::cout << email_address << '\n';
    
    return 0;
}

[e-mail]
Program ended with exit code: 0

[laura fidarova]

thank you guys so much :)

[seeplus]

Also:

#include <string>
#include <algorithm>
#include <iostream>
#include <iterator>

std::string get_email_address(const std::string& str)
{
	const auto fndat {std::find(str.cbegin(), str.cend(), '@')};
	return std::string(std::find(std::reverse_iterator<decltype(str.cbegin())>(fndat), str.crend(), ' ').base(), std::find(fndat + 1, str.cend(), ' '));
}

int main()
{
	const std::string test_str {"hgg gcgchj jkvvhc [e-mail] igvjbkn gvjkh"};

	std::cout << get_email_address(test_str) << '\n';
}

[e-mail]