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Add ∅ (empty set) as synonym for Set{Any}({})
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@jiahao
jiahao committed Apr 19, 2014
1 parent fae924a commit 67ce8b5
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1 change: 1 addition & 0 deletions base/exports.jl
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Expand Up @@ -108,6 +108,7 @@ export
WeakRef,
Woodbury,
Zip,
∅,

# Ccall types
Cchar,
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1 change: 1 addition & 0 deletions base/set.jl
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Expand Up @@ -5,6 +5,7 @@ type Set{T}
Set(itr) = union!(new(Dict{T,Nothing}()), itr)
end
Set() = Set{Any}()
∅ = Set()
Set(itr) = Set{eltype(itr)}(itr)

show(io::IO, s::Set) = (show(io, typeof(s)); show_comma_array(io, s,"({","})"))
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6 comments on commit 67ce8b5

@StefanKarpinski
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This is probably a bad idea since this is just one instance of an empty set and it is mutable. Someone is going to do is this:

whosits = ∅
for thing in whatsits
    isfrobnish(thing) && push!(whosits, thing)
end

Now ∅ isn't empty. What you really want here is for ∅ to be syntax for Set() but I'm not sure that's worth it.

@jiahao
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@jiahao jiahao commented on 67ce8b5 Apr 19, 2014

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That example reads to me like 'start with the empty set and add stuff to it', which seems fine to me.

@StefanKarpinski
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Only if there's only a single piece of code that ever wants to use the empty set. This is shared global mutable state, it's no good.

@jiahao
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@jiahao jiahao commented on 67ce8b5 Apr 19, 2014

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Ah, good point.

@kmsquire
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@kmsquire kmsquire commented on 67ce8b5 Apr 19, 2014 via email

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@kmsquire kmsquire commented on 67ce8b5 Apr 19, 2014 via email

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