p-ranav/pprint

Pretty Printer for Modern C++

Highlights

• Single header file
• Requires C++17
• MIT License

Quick Start

Simply include pprint.hpp and you're good to go.

#include <pprint.hpp>

To start printing, create a PrettyPrinter

pprint::PrettyPrinter printer;

You can construct a PrettyPrinter with any stream that inherits from std::ostream , e.g, std::stringstream

std::stringstream stream;
pprint::PrettyPrinter printer(stream);

Fundamental Types

printer.print(5);
printer.print(3.14f);
printer.print(2.718);
printer.print(true);
printer.print('x');
printer.print("Hello, 世界");
printer.print(nullptr);

5
3.14f
2.718
true
x
Hello, 世界
nullptr

Strings

Maybe you want your strings to be quoted? Simply set printer.quotes(true)

printer.quotes(true);
printer.print("A", "B", "C");

"A" "B" "C"

Complex Numbers

using namespace std::complex_literals;
std::complex<double> foo = 1. + 2.5i;
std::complex<double> bar = 9. + 4i;
printer.print(foo, "*", bar, "=", (foo * bar));   // parameter packing

(1 + 2.5i) * (9 + 4i) = (-1 + 26.5i)

Enumeration Types

enum Color { RED = 2, BLUE = 4, GREEN = 8 };
Color color = BLUE;
printer.print(color);

4

If you compile with

• Clang/LLVM >= 5
• Visual C++ >= 15.3 / Visual Studio >= 2017
• Xcode >= 10.2
• GCC >= 9

then pprint will print the name of the enum for you (thanks to magic_enum)

enum Level { LOW, MEDIUM, HIGH };
Level current_level = MEDIUM;
std::cout << "Current level: ";
printer.print(current_level);

Current level: MEDIUM

STL Sequence Containers

pprint supports a variety of STL sequence containers including std::vector, std::list, std::deque, and std::array.

Here's an example pretty print of a simple 3x3 matrix:

typedef std::array<std::array<int, 3>, 3> Mat3x3;
Mat3x3 matrix;
matrix[0] = {1, 2, 3};
matrix[1] = {4, 5, 6};
matrix[2] = {7, 8, 9};
printer.print("Matrix =", matrix);

Matrix = [
  [1, 2, 3], 
  [4, 5, 6], 
  [7, 8, 9]
]

Compact Printing

pprint also supports compact printing of containers. Simply call printer.compact(true) to enable this:

std::vector<std::map<std::string, int>> foo {{{"a", 1}, {"b", 2}}, {{"c", 3}, {"d", 4}}};
printer.compact(true);
printer.print("Foo =", foo);

Foo = [{a : 1, b : 2}, {c : 3, d : 4}]

STL Associative Containers

Support for associative containers includes pretty printing of std::map, std::multimap, std::unordered_map, std::unordered_multimap, std::set, std::multiset, std::unordered_set and , std::unordered_multiset

printer.print(std::map<std::string, std::set<int>>{ 
    {"foo", {1, 2, 3, 3, 2, 1}}, {"bar", {7, 6, 5, 4}}});

{
  "bar" : {4, 5, 6, 7}, 
  "foo" : {1, 2, 3}
}

STL Container Adaptors

pprint can print container adaptors including std::queue, std::priority_queue and std::stack. Here's an example print of a priority queue:

std::priority_queue<int> queue;
for(int n : {1,8,5,6,3,4,0,9,7,2}) queue.push(n);
printer.print(queue);

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

Fixed-size Heterogeneous Tuples

auto get_student = [](int id) {
  if (id == 0) return std::make_tuple(3.8, 'A', "Lisa Simpson");
  if (id == 1) return std::make_tuple(2.9, 'C', "Milhouse Van Houten");
  if (id == 2) return std::make_tuple(1.7, 'D', "Ralph Wiggum");
  throw std::invalid_argument("id");
};
printer.print({ get_student(0), get_student(1), get_student(2) });

{(1.7, 'D', "Ralph Wiggum"), (2.9, 'C', "Milhouse Van Houten"), (3.8, 'A', "Lisa Simpson")}

Type-safe Unions

// Construct a vector of values
std::vector<std::variant<bool, int, int *, float, std::string, std::vector<int>,		      
       std::map<std::string, std::map<std::string, int>>, 
       std::pair<double, double>>> var;
var.push_back(5);
var.push_back(nullptr);
var.push_back(3.14f);
var.push_back(std::string{"Hello World"});
var.push_back(std::vector<int>{1, 2, 3, 4});
var.push_back(std::map<std::string, std::map<std::string, int>>{{"a",{{"b",1}}}, {"c",{{"d",2}, {"e",3}}}});
var.push_back(true);
var.push_back(std::pair<double, double>{1.1, 2.2});

// Print the vector
pprint::PrettyPrinter printer;
printer.indent(2);
printer.quotes(true);
printer.print(var);

[
  5, 
  nullptr,
  3.14f, 
  "Hello World", 
  [1, 2, 3, 4], 
  {"a" : {"b" : 1}, "c" : {"d" : 2, "e" : 3}}, 
  true, 
  (1.1, 2.2)
]

Optional Values

std::optional<int> opt = 5;
std::optional<int> opt2;

printer.print(opt);
printer.print(opt2);

5
nullopt

Class Objects

pprint print class objects with or without an overloaded << operator

class Foo {};
Foo foo;
printer.print(foo);

<Object main::Foo>

If an << operator is available, pprint will use it to print your object:

class Date {
  unsigned int month, day, year;
public:
  Date(unsigned int m, unsigned int d, unsigned int y) : month(m), day(d), year(y) {}
  friend std::ostream& operator<<(std::ostream& os, const Date& dt);
};

    
std::ostream& operator<<(std::ostream& os, const Date& dt) {
  os << dt.month << '/' << dt.day << '/' << dt.year;
  return os;
}

Date date(04, 07, 2019);
printer.print("Today's date is", date);

Today's date is 4/7/2019

User-defined types

Here's an example to print user-defined types. Let's say you want to print Mesh objects

struct Vector3 {
  float x, y, z;
};

struct Mesh {
  std::vector<Vector3> vertices;
};

First, overload the << operator for these structs:

std::ostream& operator<<(std::ostream& os, const Vector3& v) {
  pprint::PrettyPrinter printer(os);
  printer.print_inline(std::make_tuple(v.x, v.y, v.z));
  return os;
}

std::ostream& operator<<(std::ostream& os, const Mesh& mesh) {
  pprint::PrettyPrinter printer(os);
  printer.print("Mesh {");
  printer.indent(2);
  printer.print_inline("vertices:", mesh.vertices);
  printer.print("}");
  return os;
}

then simply call printer.print(Mesh)

Mesh quads = {{
  {0, 0, 0}, {1, 0, 0}, {1, 1, 0}, {0, 0, 0}, {1, 1, 0}, {0, 1, 0},
  {0, 0, 1}, {1, 0, 1}, {1, 1, 1}, {0, 0, 1}, {1, 1, 1}, {0, 1, 1},
  }};

pprint::PrettyPrinter printer;
printer.print(quads);

Mesh {
  vertices: [
      (0, 0, 0), 
      (1, 0, 0), 
      (1, 1, 0), 
      (0, 0, 0), 
      (1, 1, 0), 
      (0, 1, 0), 
      (0, 0, 1), 
      (1, 0, 1), 
      (1, 1, 1), 
      (0, 0, 1), 
      (1, 1, 1), 
      (0, 1, 1)
  ]
}

License

The project is available under the MIT license.

pprint's Issues

Doesn't compile when printing std::unordered_set

This test case can't compile w/ Apple clang version 11.0.0 or gcc 8.3.0.

TEST_CASE("Print empty set (line_terminator = '\n', indent = 2)",
	  "[std::unordered_set]") {
  std::unordered_set<int> foo {};

  std::stringstream stream;
  pprint::PrettyPrinter printer(stream);
  printer.print(foo);

  const std::string expected = "{}\n";

  REQUIRE(stream.str() == expected);
}

Enable CMake release

1. Include CMakeLists.txt in the archive
2. Add pprintConfigVersion.cmake
3. Fix inconsistency: CMake install to <pprint/pprint.hpp>, not <pprint.hpp>.

[SOLVED] Printing hex numbers

Tried to define a specific operator for uint to be printed as hex in my client code:

std::ostream& operator<<(std::ostream& os, const uint64_t& uNum) {
  os << std::hex << uNum << std::dec;
  return os;
}

But it fails with

src/ext/pprint/pprint.hpp:526:43: error: ambiguous overload for 'operator<<' (operand types are 'std::basic_ostream<char>' and 'long unsigned int')
  526 |       stream_ << std::string(indent, ' ') << value << line_terminator;
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~

Is there maybe already a way to print integers in hex format?

Compiling with structopt fails

It seems like including both <pprint.hpp> and <structopt/structopt.hpp> will lead to conflicts, as magic_enum gets redefined.
Is there a standard way to use both pprint and structopt or am I missing something obvious?

Newlines, quotes, escape characters, etc in strings?

I'm not sure what's the intended behavior, but this library doesn't seem to do anything special to handle quotes or newlines or other "special" characters within strings.

int main() {
  pprint::PrettyPrinter printer;
  printer.print("x'x\"x");
  printer.print("x\nx\nx");
}

It produces just the contents of the string with quotes. Is this intended behavior?

Fatal Error: <Variant> No such file or Directory

I've used both Gcc 6.2.0 and Gcc 11.2.0 but I am getting the same error every time.

Add canon support

The title says it all...

Using this lib in corporate invironments requires using packaging instead of copy pasting code due to software clearing... so conan and cmake would be great...

Print with color