Skip to content
Convenient print statement for C++
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.

An implementation of a print statement in C++.

#include "print.h"

print expression[, expression]*
print "format" % expression[, expression]*
eprint expression[, expression]*
eprint "format" % expression[, expression]*

/** examples **/
print "Hello", "world", time(0);       // Hello world 1360826578
print "name=%q age=%s" % "Alex", 26;   // name="Alex" age=26

int numbers[] = { 1, 2, 3 };
print numbers;                         // [1, 2, 3]

std::vector<std::string> things = {"apples", "oranges", "elephants"};
print things;                          // [apples, oranges, elephants]

The first form converts each expression into a string and prints it to standard output, with each expression separated by a space and a terminating newline at the end. eprint is similar except it prints to standard error.

The second form uses a format string similar to printf().

  • %s The argument is printed directly.
  • %q The argument is quoted.

Expressions are converted to strings according to their type, as follows:

  • char* are output as NUL-terminated strings like %s.
  • int, short, long, signed char, unsigned char are printed in decimal notation like with %d.
  • char prints the charcter like %c.
  • void * or any other kind of pointers prints ths pointer in hex like %p.
  • double, float prints the number in decimal notation like %g.
  • bool prints 'true' or 'false'
  • A type that defines a member function called c_str() is converted to a string by calling this function.
  • A type than can be streamed to an std::ostream like std::cout << thing but does not have a c_str() member function is converted to a string using <<.
  • A type that has a begin() member function that returns in iterator but does not have a c_str() member function is printed like a list, e.g. ["one", "two"].
  • std:map, std::unordered_map, std::multimap, std::unordered_multipmap, QHash, QMap, QMultiHash, QMultiMap are special-cased and printed like dictionaries, e.g. {"foo": "bar"}.
  • QString is printed as a string.
  • std::pair is rendered as ("first", "second").


The easiest way to use this is to clone this repo and copy the file print.h into your project. Then simply

#include "print.h"` 

at the top of the file, but after the system #includess.


print is thread and exception safe. The output stream is locked once before anything is printed and then unlocked at the end inside a destructor. This ensures that the whole line will be printed without being interleaved with output from another thread.

Internally, the fwrite() family of function from C standard library are used for output. C++ streams are not used at all.

In benchmakrs print is a little bit faster than cout and a little bit slower than printf.

print.h includes stdio.h and nothing else.

You can’t perform that action at this time.