C++ boost::algorithm::string::trim_left()
trim_left():
This function is included in the "boost/algorithm/string" library. This library contains some brilliant methods which help in accomplishing string manipulations that are lacking in STL library.
This function "trim_left" is used to remove all the leading white-spaces in the string i.e., all the spaces present on the left side of the string as shown in the below examples:
Examples:
1. Original String: " Hello nice to meet you"
Modified String: "Hello nice to meet you"
2. Original String: " You are using boost "
Modified String: "You are using boost "
header file:
boost/algorithm/string.hpp
syntax:
trim_left(input , loc);
parameters:
input : an input sequence
loc : a locale used for space classification
The modification of the string is done in-place if trim_left() is used.
There is another variation present i.e., trim_left_copy() , which takes the same parameters as input, but instead of modifying the string in-place it returns a copy of the modified string while keeping the original string as it is.
SAMPLE CODE:
using namespace std;
using namespace boost::algorithm;
int main()
{
string s1 = " Welcome to Boost ";
string s2 = s1; //storing another copy of string s1 in s2
string s3 = " You are using boost library";
//trimming only the string s2
trim_left(s2);
//trimming s3 and storing the modified copy in newString
string newString = trim_left_copy(s3);
cout<<"EXAMPLE 1"<<endl;
cout<<"The original string: ";
cout<<s1<<endl;
cout<<"The modified string: ";
cout<<s2<<endl;
cout<<"EXAMPLE 2"<<endl;
cout<<"The original string: ";
cout<<s3<<endl;
cout<<"The modified string: ";
cout<<newString<<endl;
}
OUTPUT:
EXPLANATION:
As we an observe from the above code that trim_left() takes any string as input and it removes all the leading whitespaces. It leaves the rest of characters and symbols untouched.
Similarly, trim_left_copy() instead of modifying the original string i.e., "s3", it returns the modified string to "newString".
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