Vinyl
Before Cassette was invented, we had to go without fancy tapes and put up with scratches and skips. Some would say it makes for a warmer sound.
This package (approximately) implements Cassette's API using interpretation rather than compilation. While very slow, it works on current Julia and has low compiler overhead, so is suitable for code-tracing and debugging use cases.
Hook functions before they run:
julia> using Vinyl: @overdub, @hook
julia> struct TraceCtx end
julia> @hook TraceCtx (f::Any)(xs...) = println("Called $(:($f($(xs...))))")
julia> @overdub TraceCtx() 1+1.0
Called (+)(1, 1.0)
Called (promote)(1, 1.0)
Called (promote_type)(Int64, Float64)
Called (promote_rule)(Int64, Float64)
Called (promote_rule)(Float64, Int64)
Called (Base.promote_result)(Int64, Float64, Union{}, Float64)
Called (promote_type)(Union{}, Float64)
Called (convert)(Float64, 1)
Called (sitofp)(Float64, 1)
Called (promote_type)(Int64, Float64)
Called (promote_rule)(Int64, Float64)
Called (promote_rule)(Float64, Int64)
Called (Base.promote_result)(Int64, Float64, Union{}, Float64)
Called (promote_type)(Union{}, Float64)
Called (convert)(Float64, 1.0)
Called (tuple)(1.0, 1.0)
Called (Core._apply)(+, (1.0, 1.0))
Called (add_float)(1.0, 1.0)
2.0Alter the behaviour of a function:
julia> using Vinyl: @overdub, @primitive
julia> prod([1,2,3,4,5])
120
julia> sum([1,2,3,4,5])
15
julia> struct MulCtx end
julia> @primitive MulCtx a * b = a + b
julia> @overdub MulCtx() prod([1,2,3,4,5])
15This package also includes an implementation of delimited continuations, because why not.
julia> using Vinyl: @reset, shift
julia> @reset 2*shift(k -> k(k(4)))
16
julia> @reset begin
for i = 1:5
_ = shift(k -> (i,k(nothing)))
end
()
end
(1, (2, (3, (4, (5, ())))))
# Hijack control flow and explore multiple branches
julia> quantum_predicate(x) = shift(k -> (k(true), k(false)))
julia> function foo(x)
quantum_predicate(x) && (x = x .+ 2)
2.*x
end
julia> k = @reset foo([1,2,3])
([6, 8, 10], [2, 4, 6])