calebzulawski/hippo

Pretty-print hierarchical information automagically

What is it?

Hippo is short for Hierarchical Information as Pretty-Printed Objects.

It is a header-only library for C++17 that makes it easy to display the contents of nested data structures in an intelligent and legible manner.

To get started, take a look at the released documentation on Read the Docs, or view the latest documentation of the master branch here.

Key features

• Out-of-the-box printers for all builtin types and most standard library types
• Printers for user-defined types created via reflection macros (class/struct and enum/enum class)
• All types, even polymorphic types, can be printed without modifying the type
• Configurable indentation level and output text column count

A simple example

Custom class types can be made printable with the reflection helper macros HIPPO_CLASS_BEGIN, HIPPO_MEMBER, and HIPPO_CLASS_END.

#include "hippo/hippo.h"
#include "hippo/std/map.h"
#include <iostream>

struct Foo {
  int a;
  int b;
};

struct Bar {
  std::map<int, Foo> foos;
};

// Make Foo printable
HIPPO_CLASS_BEGIN(Foo)
HIPPO_MEMBER(a)
HIPPO_MEMBER(b)
HIPPO_CLASS_END()

// Make Bar printable
HIPPO_CLASS_BEGIN(Bar)
HIPPO_MEMBER(foos)
HIPPO_CLASS_END()

int main() {
  Bar bar;
  bar.foos[1] = Foo{0, 0};
  bar.foos[2] = Foo{1, 2};

  hippo::configuration config;
  config.indent = 2; // 2 spaces per indentation

  std::cout << "Expanded:" << std::endl;
  config.width = 0; // keep output as narrow as possible
  hippo::print_to(std::cout, bar, config);

  std::cout << "Condensed:" << std::endl;
  config.width = 80; // try to keep output under 80 chars
  hippo::print_to(std::cout, bar, config);
  return 0;
}

When run, this program produces:

Expanded:
Bar {
  foos: std::map [
    (
      key: 1,
      value: Foo {
        a: 0,
        b: 0
      }
    ),
    (
      key: 2,
      value: Foo {
        a: 1,
        b: 2
      }
    )
  ]
}
Condensed:
Bar {
  foos: std::map [
    ( key: 1, value: Foo { a: 0, b: 0 } ),
    ( key: 2, value: Foo { a: 1, b: 2 } )
  ]
}

Logo

"hippo" by Ed Harrison licensed under CC BY 3.0