Question

参考本段：

已安装（pkg）→无效| VERSIONNUMBER
If pkg is installed, return the installed version number, otherwise return nothing.

Pkg.installed("anInvalidPackage")函数应返回nothing，但会抛出错误：

julia> VERSION
v"0.5.0"
julia> Pkg.installed("anInvalidPackage")
ERROR: anInvalidPackage is not a package (not registered or installed)
 in installed(::String) at .\pkg\entry.jl:123
 in (::Base.Pkg.Dir.##2#3{Array{Any,1},Base.Pkg.Entry.#installed,Tuple{String}})
() at .\pkg\dir.jl:31
 in cd(::Base.Pkg.Dir.##2#3{Array{Any,1},Base.Pkg.Entry.#installed,Tuple{String}
}, ::String) at .\file.jl:48
 in #cd#1 at .\pkg\dir.jl:31
 in installed(::String) at .\pkg\pkg.jl:129

编辑：issue

Answer 1

如果我们在基础上查看Pkg模块的源代码，它应该使用一些线索：

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</div>

从最后两行我们可以看出，如果包未注册或已安装，Julia将抛出错误。但是，如果包已注册但未安装，则不会引发任何错误并返回function installed(pkg::AbstractString) avail = Read.available(pkg) if Read.isinstalled(pkg) res = typemin(VersionNumber) ### some libgit2 stuff ### end isempty(avail) && throw(PkgError("$pkg is not a package (not registered or installed)")) return nothing # registered but not installed end。

所以

nothing

可是：

var = Pkg.installed("AMD") # returns nothing for me as I don't have AMD installed
                           # but it is a registered package

我同意文档应该更清楚......

Pkg.installed（“anInvalidPackage”），什么都不返回或抛出错误？

1 个答案: