Formatting C++ Console Output.

Question

I've been trying to format the output to the console for the longest time and nothing is really happening. I've been trying to use as much of iomanip as I can and the ofstream& out functions.

void list::displayByName(ostream& out) const
{
 node *current_node  = headByName;

 // I have these outside the loop so I dont write it everytime.

 out << "Name\t\t" << "\tLocation" << "\tRating " << "Acre" << endl;
 out << "----\t\t" << "\t--------" << "\t------ " << "----" << endl;

 while ( current_node )
 {
  out << current_node->item.getName()// equivalent tabs dont work?
      << current_node->item.getLocation()
   << current_node->item.getAcres()  
   << current_node->item.getRating()
   << endl;

  current_node = current_node->nextByName;
 }

// The equivalent tabs do not work because I am writing names, 
// each of different length to the console. That explains why they
// are not all evenly spaced apart.
}

Is their anything That I can use to get it all properly aligned with each other? The Functions that Im calling are self-explanatory and all of different lengths, so that don't align very well with each other.

I've tried just about everything in iomanip.

Answer 1

You can write a procedure that always print the same number of characters in the standard output. something like

string StringPadding(string original, size_t charCount )
{
    original.resize( charCount, ' ' ); 
    return original;
}

and then use like this in your program

void list::displayByName(ostream& out) const
{
    node *current_node  = headByName;

    out << StringPadding( "Name", 30 ) 
        << StringPadding( "Location", 10 )
        << StringPadding( "Rating", 10 )
        << StringPadding( "Acre", 10 ) << endl;
    out << StringPadding( "----", 30 ) 
        << StringPadding( "--------", 10 )
        << StringPadding( "------", 10 )
        << StringPadding( "----", 10 ) << endl;

    while ( current_node )
    {
        out << StringPadding( current_node->item.getName(), 30 )
            << StringPadding( current_node->item.getLocation(), 10 )
            << StringPadding( current_node->item.getRating(), 10 )
            << StringPadding( current_node->item.getAcres(), 10 )
            << endl;
        current_node = current_node->nextByName;
    }
}

Answer 2

Give up on the tabs. You should be able to use io manipulators to set the field width, the fill character, and the format flag (to get left or right justification). Use the same values for the headings as you do for the data, and everything should come out nicely.

Also beware that you've switched Rating and Acres in your example.

Answer 3

Boost has a format library that allows you to easily format the ourput like the old C printf() but with type safety of C++.

Remember that the old C printf() allowed you to specify a field width. This space fills the field if the output is undersized (note it does not cope with over-sized fields).

#include <iostream>
#include <iomanip>
#include <boost/format.hpp>

struct X
{  // this structure reverse engineered from
   // example provided by 'Mikael Jansson' in order to make this a running example

    char*       name;
    double      mean;
    int         sample_count;
};
int main()
{
    X   stats[] = {{"Plop",5.6,2}};

    // nonsense output, just to exemplify

    // stdio version
    fprintf(stderr, "at %p/%s: mean value %.3f of %4d samples\n",
            stats, stats->name, stats->mean, stats->sample_count);

    // iostream
    std::cerr << "at " << (void*)stats << "/" << stats->name
              << ": mean value " << std::fixed << std::setprecision(3) << stats->mean
              << " of " << std::setw(4) << std::setfill(' ') << stats->sample_count
              << " samples\n";

    // iostream with boost::format
    std::cerr << boost::format("at %p/%s: mean value %.3f of %4d samples\n")
                % stats % stats->name % stats->mean % stats->sample_count;
}