std::set

Although there is a direct conceptual mapping between a std::set and a Ruby Set, Rice does not copy a C++ set to an Ruby set. Instead, it wraps std::set.

There are multiple reasons for this:

  • std::set instantiations can only contain one type, while Ruby Sets can contain different types

  • std::set instances can be quite large

  • std::set instances commonly contain C++ classes that have complex copy or move semantics

  • having two disconnected copies of data, one in C++ and one in Ruby, is usually undesirable

Rice will automatically define Ruby classes for each instantiation of std::set it finds. You may also manually define Ruby classes via the use of the define_set method. Set classes are added to the Std module.

Usage

For C++ methods that take set arguments, you can instantiate a new set from Ruby (see Automatically Generated Ruby Classes).

For example, assume this C++ code:

void passSet(std::set<int> ints)
{
}

define_global_function("pass_set", &passSet);

One way to call it from Ruby is like this:

set = Std::Set≺int≻.new
set.push(37)
pass_set(set)

In this case, Ruby is wrapping a C++ set. Therefore any changes made to the set in C++ will be visible to Ruby.

A second way is to pass a Ruby Set like this:

set = Set.new([3, 5, 9])
pass_set(set)

In this case, Rice will copy the Ruby array instead of wrapping it. Thus any modifications made in C++ will not be visible to Ruby.

Ruby API

Rice tries to make a std::set look like a Ruby Set by defining an API that is a subset of Set. However, there are differences you need to keep in mind.

If the set type supports C++ streams, then the following method will work, otherwise it will return “Not Printable”

  • set#to_s