tani / ruby-cont

Cont

Overview

The Cont module is a Ruby library that provides an implementation of continuations using the fiber library. Continuations are advanced control flow constructs that allow you to save the state of a computation at a certain point and then resume it later. This library is useful for managing complex control flows and implementing advanced features like coroutines, generators, and cooperative multitasking.

Installation

To use the Cont library, simply require it in your Ruby project:

require 'cont'

Usage

Cont.reset

Cont.reset limits the continuation to the current block. It takes a block of code and returns the result of that block.

Example

result = Cont.reset do
  42
end
puts result # => 42

Cont.shift

Cont.shift captures the current continuation and allows you to resume it. It takes a block of code, which should call a lambda to resume the continuation.

Example

result = Cont.reset do
  Cont.shift do |k|
    k.call(42) + 1
  end
end
puts result # => 43

Cont.reset_at

Cont.reset_at limits the continuation to the current block and assigns it a tag. It takes a tag and a block of code, allowing you to manage multiple continuation points.

Example

result = Cont.reset_at(:x) do
  1 + Cont.shift_at(:x) { |cont| cont.call(2) }
end
puts result # => 3

Cont.shift_at

Cont.shift_at captures the current continuation associated with a specific tag and allows you to resume it. It takes a tag and a block of code, enabling more complex control flow by using multiple continuations.

Example

result = Cont.reset_at(:x) do
  Cont.shift_at(:x) do |k|
    k.call(42) + 1
  end
end
puts result # => 43

Exceptions

Cont::DeadContinuationError

This exception is raised when an attempt is made to resume a dead continuation.

Cont::UnexpectedStatusError

This exception is raised when an unexpected status is encountered.

License

MIT License

Copyright (c) 2024 Masaya Taniguchi