JuliaCollections / JuliaCollections/IterTools.jl

Collect subsets of tuple

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Dominant language
Julia
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Description

Is this a bug in IterTools?

julia> using IterTools
julia> collect(subsets((0,2,6), 2))

ERROR: MethodError: Cannot `convert` an object of type Tuple{Int64,Int64} to an object of type Array{Int64,1}
...
Stacktrace:
 [1] setindex!(::Array{Array{Int64,1},1}, ::Tuple{Int64,Int64}, ::Int64) at ./array.jl:767
 [2] copyto!(::Array{Array{Int64,1},1}, ::IterTools.Binomial{Tuple{Int64,Int64,Int64}}) at ./abstractarray.jl:671
 [3] _collect at ./array.jl:550 [inlined]
 [4] collect(::IterTools.Binomial{Tuple{Int64,Int64,Int64}}) at ./array.jl:544
 [5] top-level scope at none:0

This works though:

julia> collect(x for x in subsets((0,2,6), 2))
3-element Array{Tuple{Int64,Int64},1}:
 (0, 2)
 (0, 6)
 (2, 6)

Julia 1.1
IterTools 1.3

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing collect(subsets((0,2,6), 2)) with Julia 1.1 and IterTools 1.3, then compare it with the generator-based collection shown in the issue. Trace the subsets iterator and collection behavior until the tuple-to-array conversion failure is located; done means direct collection returns the expected three tuples without the MethodError.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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