Test for existence of a variable

[kristoffer.carlsson]

@compleat

To me, that seems too abstract.
I was thinking about the situation where x had not been defined. Then:

julia> @isdefined x
false

julia> x=2
2

julia> @isdefined x
true

For a ‘newbie’ (like my students, and even me) this seems much simpler to visualise.

I mean, that’s exactly what it shows? First when x is not defined, and then when it is defined.