Dict get destroys global variable?

[K leo]

Calling "get" anywhere in a function makes a global variable undefined.  Can anyone please help explaining the following?

1) without calling "get", the global variable is fine:

a=0

Dicta = Dict{Int,Int}()

function testGlobal()

    println(a)

    merge!(Dicta, Dict(1=>1))

#     a=get(Dicta, 1, 0)

    println(a)  

    nothing

end

julia> testGlobal()

0

0

2) calling "get" (same code as above except uncommenting the "get" statement) and the global variable becomes undefined:

a=0

Dicta = Dict{Int,Int}()

function testGlobal()

    println(a)

    merge!(Dicta, Dict(1=>1))

    a=get(Dicta, 1, 0)

    println(a)  

    nothing

end

julia> testGlobal()

ERROR: UndefVarError: a not defined

 in testGlobal() at /xxx/testType.jl:4

3) not calling the first println, the code works, but the global a is not set:

a=0

Dicta = Dict{Int,Int}()

function testGlobal()

#     println(a)

    merge!(Dicta, Dict(1=>1))

    a=get(Dicta, 1, 0)

    println(a)  

    nothing

end

julia> testGlobal()

1

[K leo]

Sorry, this is not related to Dict at all.  If I replace the "a=get..." statement with simply "a=2", the global variable is no longer accessible.  What is wrong?

[Isaiah Norton]

Use `global a = ...`

Please see: http://docs.julialang.org/en/latest/manual/variables-and-scoping/#hard-local-scope

global variables are only inherited for reading but not for writing

 

[K leo]

Thank you Isaiah for pointing that out!