sum(i for i in Vector{Int}()) raises an error: ERROR: MethodError: no method matching zero(::Type{Any}) Closest candidates are: zero(::Type{Base.LibGit2.Oid}) at libgit2/oid.jl:88 zero(::Type{Base.Pkg.Resolve.VersionWeights.VWPreBuildItem}) at pkg/resolve/versionweight.jl:80 zero(::Type{Base.…

See also the related issue https://github.com/JuliaLang/julia/issues/18695 and https://github.com/JuliaLang/julia/issues/18645

Is there / shouldn’t there be a way to specify the eltype of a generator? What’s the equivalent of sum(Int[i for i in Vector{Int}()])

Something like sum(f(x)::Int for x in Vector()) should tell the compiler that the generator’s eltype is an Int. Currently it raises the same error (julia v0.5.0).

I defined a “safe sum” that guarantees a return type and returns the correct 0 for empty iterators: function sumf(::Type{T}, itr)::T where T isempty(itr) ? zero(T) : sum(x::T for x in itr)::T end Perhaps this should be added as a method to Base.sum?

Note that while it may be useful, adding it to sum would conflict with the existing sum(::Union{Function, Type}, ::Any) method.

You can always call reduce instead.

Sum(i for i in Vector{Int}()) raises error instead of returning 0?

General Usage

e3c6 June 25, 2018, 11:15am 8

https://github.com/JuliaLang/julia/issues/27766

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Sum(i for i in Vector{Int}()) raises error instead of returning 0?

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