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C++ alignment when printing cout <<
(7 answers)
Closed 8 years ago.
I want output as per follows in C++:
name aabsd
Size in KB 170
Width and Height 512 512
cout<<"\n \t name "<<std::setw(15)<<filename;
cout<<" \n \t Size in KB "<<std::setw(10)<<size;
cout<< " \n \t Width and Height "<<std::setw(3)<<width<<" "<<height;
Values on right side should be aligned in same coloumn. I tried with setw() but it does not give me output aligned because my left side text is different.
Another answer that relies on purely C++ specific constructs.
#include <iostream>
#include <iomanip>
int main()
{
char const* filename = "abcd";
int size = 10;
double width = 20;
double height = 30;
// std::left says align the output to the left when writing the next field
// set::setw(20) says use 20 characters for the next field.
std::cout << std::left << std::setw(20) << "name" << filename << std::endl;
std::cout << std::left << std::setw(20) << "Size in KB" << size << std::endl;
std::cout << std::left << std::setw(20) << "Width and Height" << width << " " << height << std::endl;
return 0;
}
printf( "%-20s%-20s", "name", "aabsd" );
printf( "%-20s%-20d", "Size in KB", 170 );
printf( "%-20s%-20d %d", "Width and Height", 512, 512 );
-20%s will left justify 20 spaces
20%s will right justify 20 spaces
Try using \t to align the output to the next tab position.
printf("Name\t%s\n",name);
printf("Size in KB\t%d\n",size);
printf("Width and Height\t%d%d\n",width,height);
That will make the second column aligned, maybe you will need a second tab in one of them, but thats it.
Another way is to manually move the cursor to where you want it. This should do
SetCursorPos(xpos,ypos);
You need to include windows.h
Related
This is my first C++ related question and I'm new to character pointers and their usage. I think I've got it down but for an assignment the required output for this program is
So each first and last name is a character pointer of 20 characters (I could probably size it down but whatever) and when I output it now it looks like
cout << stu[i]->first << " " << stu[i]->last << " " << (float)stu[i]->mean << endl; and outputs the same thing as above but with a single space between each piece of data. How would I get it to print out the whitespace of the rest of the char pointer so it creates nice neat columns?
Thanks!
There is no magic whitespace in memory a char* points to. If you want to align your output you could use std::setw():
#include <iostream>
#include <iomanip>
int main()
{
char const *foo{ "Jamie" };
char const *bar{ "Reynolds" };
std::cout << std::setw(10) << foo << std::setw(10) << bar << '\n';
}
I'm working on an assignment where I need to print out the ASCII table in the table format exactly like the picture below.
http://i.gyazo.com/f1a8625aad1d55585df20f4dba920830.png
I currently can't get the special words/symbols to display (8, 9, 10, 13, 27, 32, 127).
Here it is running:
http://i.gyazo.com/80c8ad48ef2993e93ef9b8feb30e53af.png
Here is my current code:
#include <iomanip>
#include <iostream>
using namespace std;
int main()
{
cout<<"ASCII TABLE:"<<endl;
cout<<endl;
for (int i = 0; i < 128; i++)
{
if (i <= 32)
cout << "|" << setw(2)
<<i
<< setw(3)
<< "^" << char (64+i) <<"|";
if (i >= 33)
cout << "|" << setw(3)
<<i
<< setw(3)
<<char (i) << "|";
if((i+1)%8 == 0) cout << endl;
}
return 0;
}
8 Back Space
9 Horizontal Tab
10 New Line
13 carriage return
27 Escape (Esc)
32 Space
127 Del
As Above these ASCII characters doesn't display any visible or printed character. That's why you might be thinking you are not getting these values.
I'm no sure what's your real problem there, but you didn't get an answer yet about how to print the special codes.
Running your programme I see that you have some minor alignment problems. If that's the problem, note that setw(3) only applies to the next element:
cout << setw(3) << "^" << char (64+i); // prints " ^A" instead of " ^A".
If you try to correct into
cout << setw(3) << "^"+ char (64+i); // ouch !!!!
you'll get undefined behaviour (garbage) because "^" is a pointer to a string and adding char(64+i) is understood as adding an offset of 64+i to this pointer. As this is a rather random address, you'll get garbage. Use a std::string instead.
The other difference I see between your programme's output and the expected result is that you don't print the code of the special chars. If that's the problem, either use a switch statement (very repetitive here), or a lot of if/else or use an associative map.
Here an alternative proposal putting all this together:
map<char, string>special{ { 8, "BS " }, { 9, "\\t " }, { 10, "\\n " }, { 13, "CR " }, { 27, "ESC" }, { 32, "SP " }, { 127, "DEL" } };
cout << "ASCII TABLE:" << endl << endl;
for (int i = 0; i < 128; i++) {
cout << "|" << setw(3)<<i<<setw(4); // setw() only applies to next
if (iscntrl(i) || isspace(i)) { // if its a control char or a space
auto it = special.find(i); // look if there's a special translation
if (it != special.end()) // if yes, use it
cout << it->second;
else cout << string("^") + char(64 + i)+ string(" "); // if not, ^x, using strings
}
else if (isprint(i)) // Sorry I'm paranoïd: but I always imagine that there could be a non printable ctrl ;-)
cout << char(i)+string(" ") ; // print normal char
cout << "|";
if ((i + 1) % 8 == 0) cout << endl;
}
Now some additional advices:
take the effort to indent
instead of manual categorization of chars, use iscntrl(), isspace(), isprint(). As long as you only use ascii, it's manageable to do like you did. But as soons as you move to internationalisation and wide chars it becomes increasinlgy cumbersome to do that whereas there are easy wide equivalents like iswcntrl(), iswspace(), iswprint().
also be rigorous on two consecutive if: If you know that only one of the two should apply, make the effort to write if ... else if these four additional lettes can save you hours of debugging later.
Is there a way to align text when printing using std::cout? I'm using tabs, but when the words are too big they won't be aligned anymore.
Sales Report for September 15, 2010
Artist Title Price Genre Disc Sale Tax Cash
Merle Blue 12.99 Country 4% 12.47 1.01 13.48
Richard Music 8.49 Classical 8% 7.81 0.66 8.47
Paula Shut 8.49 Classical 8% 7.81 0.72 8.49
The ISO C++ standard way to do it is to #include <iomanip> and use io manipulators like std::setw. However, that said, those io manipulators are a real pain to use even for text, and are just about unusable for formatting numbers (I assume you want your dollar amounts to line up on the decimal, have the correct number of significant digits, etc.). Even for just plain text labels, the code will look something like this for the first part of your first line:
// using standard iomanip facilities
cout << setw(20) << "Artist"
<< setw(20) << "Title"
<< setw(8) << "Price";
// ... not going to try to write the numeric formatting...
If you are able to use the Boost libraries, run (don't walk) and use the Boost.Format library instead. It is fully compatible with the standard iostreams, and it gives you all the goodness for easy formatting with printf/Posix formatting string, but without losing any of the power and convenience of iostreams themselves. For example, the first parts of your first two lines would look something like:
// using Boost.Format
cout << format("%-20s %-20s %-8s\n") % "Artist" % "Title" % "Price";
cout << format("%-20s %-20s %8.2f\n") % "Merle" % "Blue" % 12.99;
Another way to make column aligned is as follows:
using namespace std;
cout.width(20); cout << left << "Artist";
cout.width(20); cout << left << "Title";
cout.width(10); cout << left << "Price";
...
cout.width(20); cout << left << artist;
cout.width(20); cout << left << title;
cout.width(10); cout << left << price;
We should estimate maximum length of values for each column. In this case, values of "Artist" column should not exceed 20 characters and so on.
IO manipulators are what you need. setw, in particular. Here's an example from the reference page:
// setw example
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << setw (10);
cout << 77 << endl;
return 0;
}
Justifying the field to the left and right is done with the left and right manipulators.
Also take a look at setfill. Here's a more complete tutorial on formatting C++ output with io manipulators.
See also: Which C I/O library should be used in C++ code?
struct Item
{
std::string artist;
std::string c;
integer price; // in cents (as floating point is not acurate)
std::string Genre;
integer disc;
integer sale;
integer tax;
};
std::cout << "Sales Report for September 15, 2010\n"
<< "Artist Title Price Genre Disc Sale Tax Cash\n";
FOREACH(Item loop,data)
{
fprintf(stdout,"%8s%8s%8.2f%7s%1s%8.2f%8.2f\n",
, loop.artist
, loop.title
, loop.price / 100.0
, loop.Genre
, loop.disc , "%"
, loop.sale / 100.0
, loop.tax / 100.0);
// or
std::cout << std::setw(8) << loop.artist
<< std::setw(8) << loop.title
<< std::setw(8) << fixed << setprecision(2) << loop.price / 100.0
<< std::setw(8) << loop.Genre
<< std::setw(7) << loop.disc << std::setw(1) << "%"
<< std::setw(8) << fixed << setprecision(2) << loop.sale / 100.0
<< std::setw(8) << fixed << setprecision(2) << loop.tax / 100.0
<< "\n";
// or
std::cout << boost::format("%8s%8s%8.2f%7s%1s%8.2f%8.2f\n")
% loop.artist
% loop.title
% loop.price / 100.0
% loop.Genre
% loop.disc % "%"
% loop.sale / 100.0
% loop.tax / 100.0;
}
At the time you emit the very first line,
Artist Title Price Genre Disc Sale Tax Cash
to achieve "alignment", you have to know "in advance" how wide each column will need to be (otherwise, alignment is impossible). Once you do know the needed width for each column (there are several possible ways to achieve that depending on where your data's coming from), then the setw function mentioned in the other answer will help, or (more brutally;-) you could emit carefully computed number of extra spaces (clunky, to be sure), etc. I don't recommend tabs anyway as you have no real control on how the final output device will render those, in general.
Back to the core issue, if you have each column's value in a vector<T> of some sort, for example, you can do a first formatting pass to determine the maximum width of the column, for example (be sure to take into account the width of the header for the column, too, of course).
If your rows are coming "one by one", and alignment is crucial, you'll have to cache or buffer the rows as they come in (in memory if they fit, otherwise on a disk file that you'll later "rewind" and re-read from the start), taking care to keep updated the vector of "maximum widths of each column" as the rows do come. You can't output anything (not even the headers!), if keeping alignment is crucial, until you've seen the very last row (unless you somehow magically have previous knowledge of the columns' widths, of course;-).
C++20 std::format options <, ^ and >
According to https://en.cppreference.com/w/cpp/utility/format/formatter#Standard_format_specification the following should hold:
#include <format>
// left: "42 "
std::cout << std::format("{:<6}", 42);
// right: " 42"
std::cout << std::format("{:>6}", 42);
// center: " 42 "
std::cout << std::format("{:^6}", 42);
The existing fmt library implements it for before it gets official support: https://github.com/fmtlib/fmt Install on Ubuntu 22.04:
sudo apt install libfmt-dev
Modify source to replace:
<format> with <fmt/core.h>
std::format to fmt::format
main.cpp
#include <iostream>
#include <fmt/core.h>
int main() {
std::cout << "123456.\n";
// left
std::cout << fmt::format("{:<6}.\n", 42);
// right
std::cout << fmt::format("{:>6}.\n", 42);
// center
std::cout << fmt::format("{:^6}.\n", 42);
}
and compile and run with:
g++ -std=c++11 -o main.out main.cpp -lfmt
./main.out
Output:
123456.
42 .
42.
42 .
More information at: std::string formatting like sprintf
The easiest way, without the use of "complex" functions, is to format by hand:
an example:
std::cout << std::setprecision(10)
<< "integral of sin(x) from x = 0 to x = pi" << '\n'
<< "approximate: " << integrate(a, b, nbins) << '\n'
<< "exact: " << 2.0 << '\n';
Sorry for the basic question, I am just starting to use QImage for reading pixel data from an image file.
To understand the member functions, I tried to load an image file and tried to output the functions return values:
QString fileName = "pic1.bmp";
QImage myImage;
myImage.load( fileName );
std::cout << "width = " << myImage.width() << std::endl;
std::cout << "height = " << myImage.height() << std::endl;
std::cout << "dotspermeterX = " << myImage.dotsPerMeterX() << std::endl;
std::cout << "dotspermeterY = " << myImage.dotsPerMeterY() << std::endl;
QRectF myRect = myImage.rect();
std::cout << "rect = " << myRect.bottomLeft().x() << "," << myRect.bottomLeft().y()
<< " " << myRect.topRight().x() << "," << myRect.topRight().y() << std::endl;
The output I got was:
width = 858
height = 608
dotspermeterX = 4724
dotspermeterY = 4724
rect = 0,608 858,0
My questions are:
1. What is the difference between dots and pixels?
2. Does QImage work only with int pixels? Can't I read sub-pixel data for better precision?
To clarify my question, Following is a zoomed bitmap image of a diagonal line and I want to read all the small pixels/dots in this line. Is this possible?
As for the "dots per meter", you probably heard of "dots per inch" (or DPI). It's the same. If, for example, you have a 20 inch monitor with the horizontal resolution of X pixels, you will have Y "dots per inch" (or pixels per inch). If you then switch to a 40 inch monitor but with the same horizontal resolution X, then you have half the number of DPI, as the screen is now double as wide. So DPI (or PPI) can be seens as a measurement of the size of the pixels.
And no, I seriously doubt that QImage have any support for sub-pixel data.
Is there a way to align text when printing using std::cout? I'm using tabs, but when the words are too big they won't be aligned anymore.
Sales Report for September 15, 2010
Artist Title Price Genre Disc Sale Tax Cash
Merle Blue 12.99 Country 4% 12.47 1.01 13.48
Richard Music 8.49 Classical 8% 7.81 0.66 8.47
Paula Shut 8.49 Classical 8% 7.81 0.72 8.49
The ISO C++ standard way to do it is to #include <iomanip> and use io manipulators like std::setw. However, that said, those io manipulators are a real pain to use even for text, and are just about unusable for formatting numbers (I assume you want your dollar amounts to line up on the decimal, have the correct number of significant digits, etc.). Even for just plain text labels, the code will look something like this for the first part of your first line:
// using standard iomanip facilities
cout << setw(20) << "Artist"
<< setw(20) << "Title"
<< setw(8) << "Price";
// ... not going to try to write the numeric formatting...
If you are able to use the Boost libraries, run (don't walk) and use the Boost.Format library instead. It is fully compatible with the standard iostreams, and it gives you all the goodness for easy formatting with printf/Posix formatting string, but without losing any of the power and convenience of iostreams themselves. For example, the first parts of your first two lines would look something like:
// using Boost.Format
cout << format("%-20s %-20s %-8s\n") % "Artist" % "Title" % "Price";
cout << format("%-20s %-20s %8.2f\n") % "Merle" % "Blue" % 12.99;
Another way to make column aligned is as follows:
using namespace std;
cout.width(20); cout << left << "Artist";
cout.width(20); cout << left << "Title";
cout.width(10); cout << left << "Price";
...
cout.width(20); cout << left << artist;
cout.width(20); cout << left << title;
cout.width(10); cout << left << price;
We should estimate maximum length of values for each column. In this case, values of "Artist" column should not exceed 20 characters and so on.
IO manipulators are what you need. setw, in particular. Here's an example from the reference page:
// setw example
#include <iostream>
#include <iomanip>
using namespace std;
int main () {
cout << setw (10);
cout << 77 << endl;
return 0;
}
Justifying the field to the left and right is done with the left and right manipulators.
Also take a look at setfill. Here's a more complete tutorial on formatting C++ output with io manipulators.
See also: Which C I/O library should be used in C++ code?
struct Item
{
std::string artist;
std::string c;
integer price; // in cents (as floating point is not acurate)
std::string Genre;
integer disc;
integer sale;
integer tax;
};
std::cout << "Sales Report for September 15, 2010\n"
<< "Artist Title Price Genre Disc Sale Tax Cash\n";
FOREACH(Item loop,data)
{
fprintf(stdout,"%8s%8s%8.2f%7s%1s%8.2f%8.2f\n",
, loop.artist
, loop.title
, loop.price / 100.0
, loop.Genre
, loop.disc , "%"
, loop.sale / 100.0
, loop.tax / 100.0);
// or
std::cout << std::setw(8) << loop.artist
<< std::setw(8) << loop.title
<< std::setw(8) << fixed << setprecision(2) << loop.price / 100.0
<< std::setw(8) << loop.Genre
<< std::setw(7) << loop.disc << std::setw(1) << "%"
<< std::setw(8) << fixed << setprecision(2) << loop.sale / 100.0
<< std::setw(8) << fixed << setprecision(2) << loop.tax / 100.0
<< "\n";
// or
std::cout << boost::format("%8s%8s%8.2f%7s%1s%8.2f%8.2f\n")
% loop.artist
% loop.title
% loop.price / 100.0
% loop.Genre
% loop.disc % "%"
% loop.sale / 100.0
% loop.tax / 100.0;
}
At the time you emit the very first line,
Artist Title Price Genre Disc Sale Tax Cash
to achieve "alignment", you have to know "in advance" how wide each column will need to be (otherwise, alignment is impossible). Once you do know the needed width for each column (there are several possible ways to achieve that depending on where your data's coming from), then the setw function mentioned in the other answer will help, or (more brutally;-) you could emit carefully computed number of extra spaces (clunky, to be sure), etc. I don't recommend tabs anyway as you have no real control on how the final output device will render those, in general.
Back to the core issue, if you have each column's value in a vector<T> of some sort, for example, you can do a first formatting pass to determine the maximum width of the column, for example (be sure to take into account the width of the header for the column, too, of course).
If your rows are coming "one by one", and alignment is crucial, you'll have to cache or buffer the rows as they come in (in memory if they fit, otherwise on a disk file that you'll later "rewind" and re-read from the start), taking care to keep updated the vector of "maximum widths of each column" as the rows do come. You can't output anything (not even the headers!), if keeping alignment is crucial, until you've seen the very last row (unless you somehow magically have previous knowledge of the columns' widths, of course;-).
C++20 std::format options <, ^ and >
According to https://en.cppreference.com/w/cpp/utility/format/formatter#Standard_format_specification the following should hold:
#include <format>
// left: "42 "
std::cout << std::format("{:<6}", 42);
// right: " 42"
std::cout << std::format("{:>6}", 42);
// center: " 42 "
std::cout << std::format("{:^6}", 42);
The existing fmt library implements it for before it gets official support: https://github.com/fmtlib/fmt Install on Ubuntu 22.04:
sudo apt install libfmt-dev
Modify source to replace:
<format> with <fmt/core.h>
std::format to fmt::format
main.cpp
#include <iostream>
#include <fmt/core.h>
int main() {
std::cout << "123456.\n";
// left
std::cout << fmt::format("{:<6}.\n", 42);
// right
std::cout << fmt::format("{:>6}.\n", 42);
// center
std::cout << fmt::format("{:^6}.\n", 42);
}
and compile and run with:
g++ -std=c++11 -o main.out main.cpp -lfmt
./main.out
Output:
123456.
42 .
42.
42 .
More information at: std::string formatting like sprintf
The easiest way, without the use of "complex" functions, is to format by hand:
an example:
std::cout << std::setprecision(10)
<< "integral of sin(x) from x = 0 to x = pi" << '\n'
<< "approximate: " << integrate(a, b, nbins) << '\n'
<< "exact: " << 2.0 << '\n';