13.7.2. Justification (left, right and internal)

Stream manipulators left and right enable fields to be left justified with padding characters to the right or right justified with padding characters to the left, respectively. The padding character is specified by the fill member function or the setfill parameterized stream manipulator (which we discuss in Section 13.7.3). Figure 13.14 uses the setw, left and right manipulators to left justify and right justify integer data in a field.

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 1   // Fig. 13.14: fig13_14.cpp
 2   // Left and right justification with stream manipulators left and right.
 3   #include <iostream>
 4   #include <iomanip>
 5   using namespace std;
 6
 7   int main()
 8   {
 9      int x = 12345;
10
11      // display x right justified (default)
12      cout << "Default is right justified:" << endl
13         << setw( 10 ) << x;
14
15      // use left manipulator to display x left justified
16      cout << " Use std::left to left justify x: "
17         << left << setw( 10 ) << x;
18
19      // use right manipulator to display x right justified
20      cout << " Use std::right to right justify x: "
21         << right << setw( 10 ) << x << endl;
22   } // end main

Default is right justified:
     12345

Use std::left to left justify x:
12345

Use std::right to right justify x:
     12345

Fig. 13.14. Left and right justification with stream manipulators left and right.

Stream manipulator internal indicates that a number’s sign (or base when using stream manipulator showbase) should be left justified within a field, that the number’s magnitude should be right justified and that intervening spaces should be padded with the fill character. Figure 13.15 shows the internal stream manipulator specifying internal spacing (line 10). Note that showpos forces the plus sign to print (line 10). To reset the showpos setting, output the stream manipulator noshowpos.

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 1   // Fig. 13.15: fig13_15.cpp
 2   // Printing an integer with internal spacing and plus sign.
 3   #include <iostream>
 4   #include <iomanip>
 5   using namespace std;
 6
 7   int main()
 8   {
 9      // display value with internal spacing and plus sign
10      cout << internal << showpos << setw( 10 ) << 123 << endl;
11   } // end main

+      123

Fig. 13.15. Printing an integer with internal spacing and plus sign.

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