Le mercredi 12 octobre 2016 01:45:25 UTC+2, Jared Crean a écrit :
>
> Very nice summary, thanks for posting. One question I had was what should
> the signature of a function be to receive a generator? For example, if the
> only method of extrema is extrema(A::AbstractArray), is that too
> restrictive?
>
> Jared Crean
>
>
Any functions working with iterables will work with generators.
julia> methods(extrema)
# 4 methods for generic function "extrema":
extrema(r::Range) at reduce.jl:345
extrema(x::Real) at reduce.jl:346
extrema(A::AbstractArray, dims) at reduce.jl:388
extrema(itr) at reduce.jl:362
The last line tells you that extrema will work. An object is iterable if it
implements the methods start, next and done. There are in fact a few other
objects that also work on generators.
julia> methodswith(Base.Generator)
8-element Array{Method,1}:
collect(itr::Base.Generator) at array.jl:298
done(g::Base.Generator, s) at generator.jl:22
indices(g::Base.Generator) at generator.jl:91
length(g::Base.Generator) at generator.jl:89
ndims(g::Base.Generator) at generator.jl:92
next(g::Base.Generator, s) at generator.jl:24
size(g::Base.Generator) at generator.jl:90
start(g::Base.Generator) at generator.jl:21
There are a few functions that work on arrays but not on iterables. You
should not expect these to work on generators.
julia> show(reverse([1:10;]))
[10,9,8,7,6,5,4,3,2,1]
julia> show(reverse(i for i = 1:10))
ERROR: MethodError: no method matching
reverse(::Base.Generator{UnitRange{Int64},##9#10})
Closest candidates are:
reverse(!Matched::String) at strings/string.jl:209
reverse(!Matched::BitArray{1}) at bitarray.jl:1416
reverse(!Matched::Tuple) at tuple.jl:199
...
