Absolute positioning in printout with cout in C++ ?

Question

How do you get "absolutely positioned" columns with cout, that leftaligns text and right-aligns numbers?

#include <iostream>
#include <iomanip>
using namespace std;

struct Human {
    char name[20];
    char name2[20];
    char name3[20];
    double pts;
};

int main() {
    int i;
    Human myHumen[3] = {
        {"Mr", "Alan", "Turing", 12.25},
        {"Ms", "Ada", "Lovelace", 15.25},
        {"Sir",  "Edgar Allan", "Poe", 45.25}
    };
    cout << "Name1" << setw(22) << "Name2" << setw(22) << "Name3" << setw(22) << "Rating" <<endl;
    cout << "-----------------------------------------------------------------------\n";
    for(i = 0; i < 3; i++) {
        cout << myHumen[i].name << setw(22) << myHumen[i].name2 << setw(22) << myHumen[i].name3 << setw(20) << myHumen[i].pts << endl;
    }//this didn't do nice printouts, with leftalign for text and rightalign with numbers
}

Answer 1

You use the "left" and "right" manipulators:

cout << std::left  << std::setw(30) << "This is left aligned"
     << std::right << std::setw(30) << "This is right aligned";

An example with text + numbers:

typedef std::vector<std::pair<std::string, int> > Vec;
std::vector<std::pair<std::string, int> > data;
data.push_back(std::make_pair("Alan Turing", 125));
data.push_back(std::make_pair("Ada Lovelace", 2115));

for(Vec::iterator it = data.begin(), e = data.end(); it != e; ++it)
{
    cout << std::left << std::setw(20) << it->first
         << std::right << std::setw(20) << it->second << "\n";
}

Which prints:

Alan Turing                          125
Ada Lovelace                        2115

Answer 2

This is going to be slightly unpopular, but you can just use printf for this kind of quick program. The formatting strings are easier to understand and use (given someone who groks both iostreams and printf).

#include <cstdio>
#include <iostream>
#include <iomanip>
#include <string>

struct Human {
  char name[20];   // consider using std::string
  char name2[20];
  char name3[20];
  double pts;
};

int main() {
  using namespace std;
  Human people[3] = {
    {"Mr", "Alan", "Turing", 12.25},
    {"Ms", "Ada", "Lovelace", 15.25},
    {"Sir",  "Edgar Allan", "Poe", 45.25}
  };
  printf("%-22s%-22s%-22s%20s\n", "Name1", "Name2", "Name3", "Rating");
  cout << string(22 * 3 + 20, '-') << '\n';
  for (int i = 0; i < 3; i++) {
    Human const& h = people[i];
    printf("%-22s%-22s%-22s%20f\n", h.name, h.name2, h.name3, h.pts);
  }
  return 0;
}

It is safe (by default, see std::sync_with_stdio) to mix cout and printf, and a good compiler can check the types of the format strings for you, too (-Wall in gcc).