10.1. Lining Up Text Output
Problem
You need to line up your text output vertically. For example, if you are exporting tabular data, you may want it to look like this:
Jim Willcox Mesa AZ Bill Johnson San Mateo CA Robert Robertson Fort Collins CO
You will probably also want to be able to right- or left-justify the text.
Solution
Use ostream or wostream, for narrow or wide characters, defined in <ostream>, and the standard stream manipulators to set the field width
and justify the text. Example 10-1 shows
how.
Example 10-1. Lining up text output
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main() {
ios_base::fmtflags flags = cout.flags();
string first, last, citystate;
int width = 20;
first = "Richard";
last = "Stevens";
citystate = "Tucson, AZ";
cout << left // Left-justify in each field
<< setw(width) << first // Then, repeatedly set the width
<< setw(width) << last // and write some data
<< setw(width) << citystate << endl;
cout.flags(flags);
}The output looks like this:
Richard Stevens Tucson, AZ
Discussion
A manipulator is a function that operates on a stream. Manipulators are applied to a
stream with operator<<. The stream’s format
(input or output) is controlled by a set of flags and settings on the ultimate base stream
class, ios_base. Manipulators exist to provide
convenient shorthand for adjusting these flags and settings without having to explicitly
set them via setf or flags, which is cumbersome to write and ugly to read. The best way ...