The match_results::length() is a inbuilt function in C++ which is used to return the length of a particular match in the match_results object.
Syntax:
smatch_name.length(n) Note: smatch_name is an object of match_results class.
Parameters: It accepts a single parameter n which specifies the Match number. It is lower than match_results::size. The match number 0 represents the entire matched expression. Subsequent match numbers identify the sub-expressions if any. The passed integral is an unsigned integral type.
Return Value:It returns the length of the n-th match in the match_results object.
Note: First element always contains the whole regex match while the others contain the particular Capturing Group.
Below programs illustrate the above function.
Program 1:
// CPP program to illustrate // match_results length() in C++ #include <bits/stdc++.h> using namespace std;
int main()
{ string s( "Geeksforgeeks" );
regex re( "(Geeks)(.*)" );
smatch match;
regex_match(s, match, re);
for ( int i = 0; i < match.size(); i++) {
cout << "match " << i << " has a length of "
<< match.length(i) << endl;
}
return 0;
} |
match 0 has a length of 13 match 1 has a length of 5 match 2 has a length of 8
Program 2:
// CPP program to illustrate // match_results length() in C++ #include <bits/stdc++.h> using namespace std;
int main()
{ string s( "Geeksforgeeks" );
regex re( "(Ge)(eks)(.*)" );
smatch match;
regex_match(s, match, re);
int max_length = 0;
string str;
// Since the first match is the
// whole string we do not consider it.
for ( int i = 1; i < match.size(); i++) {
if (match.length(i) > max_length) {
str = match[i];
max_length = match.length(i);
}
}
cout << "max-length sub match is " << str
<< " with a length of " << max_length;
return 0;
} |
max-length sub match is forgeeks with a length of 8