ResumableFunctions

C# has a convenient way to create iterators using the yield return statement. The package ResumableFunctions provides the same functionality for the Julia language by introducing the @resumable and the @yield macros. These macros can be used to replace the Task switching functions produce and consume which were deprecated in Julia v0.6. Channels are the preferred way for inter-task communication in julia v0.6+, but their performance is subpar for iterator applications. See the benchmarks section below.

Build Status & Coverage

Installation

ResumableFunctions is a registered package and can be installed by running:

using Pkg
Pkg.add("ResumableFunctions")

Documentation

using ResumableFunctions

@resumable function fibonnaci(n::Int) :: Int
  a = 0
  b = 1
  for i in 1:n
    @yield a
    a, b = b, a+b
  end
end

for fib in fibonnaci(10)
  println(fib)
end

Benchmarks

The following block is the result of running julia --project=. benchmark/benchmarks.jl on a computer with the processor: Intel(R) Core(TM) i5-5300U CPU @ 2.30GHz. Julia version 1.1.1 was used.

Direct:
  49.724 ns (0 allocations: 0 bytes)
ResumableFunctions:
  10.230 μs (281 allocations: 8.83 KiB)
Channels csize=0:
  305.877 μs (465 allocations: 8.84 KiB)
Channels csize=1:
  504.438 μs (379 allocations: 7.33 KiB)
Channels csize=20:
  87.889 μs (206 allocations: 5.06 KiB)
Channels csize=100:
  67.911 μs (198 allocations: 6.44 KiB)
Closure:
  2.437 μs (83 allocations: 1.31 KiB)
Closure optimised:
  245.676 ns (3 allocations: 64 bytes)
Closure statemachine:
  40.149 ns (0 allocations: 0 bytes)
Iteration protocol:
  63.635 ns (0 allocations: 0 bytes)

Licence & References

Authors

Ben Lauwens, Royal Military Academy, Brussels, Belgium.

Contributing

To discuss problems or feature requests, file an issue. For bugs, please include as much information as possible, including operating system, julia version, and version of MacroTools.
To contribute, make a pull request. Contributions should include tests for any new features/bug fixes.

Release notes

2019: v0.5.1
- inference problem solved: force iterator next value to be of type Union of Tuple and Nothing.
2019: v0.5.0 is Julia v1.2 compatible
2018: v0.4.2 prepare for Julia v1.1
- better inference caused a problem;).
- iterator with a specified rtype is fixed.
2018: v0.4.0 is Julia v1.0 compatible.
2018: v0.3.1 uses the new iteration protocol.
- the new iteration protocol is used for a @resumable function based iterator.
- the for loop transformation implements also the new iteration protocol.
2018: v0.3 is Julia v0.7 compatible.
- introduction of let block to allow variables not te be persisted between @resumable function calls (EXPERIMENTAL).
- the eltype of a @resumable function based iterator is its return type if specified, otherwise Any.
2018: v0.2 the iterator now behaves as a Python generator: only values that are explicitely yielded are generated; the return value is ignored and a warning is generated.
2017: v0.1 initial release that is Julia v0.6 compatible:
- Introduction of the @resumable and the @yield macros.
- A @resumable function generates a type that implements the iterator interface.
- Parametric @resumable functions are supported.

Caveats

In a try block only top level @yield statements are allowed.
In a finally block a @yield statement is not allowed.
An anonymous function can not contain a @yield statement.

UnofficialJuliaMirror / ResumableFunctions.jl-c5292f4c-5179-55e1-98c5-05642aab7184