Indexing 0-based JuMPArray: end keyword throws errors

[dourouc05]

When I ran code on an updated JuMP (0.12), indexing arrays of variables at [end] stopped working (while this code perfectly worked in JuMP 0.11). Here is a

using JuMP

m = Model()
@defVar(m, x[0:2], Bin)
@setObjective(m, Max, x[1])
solve(m)

getValue(x[end])
getValue(x)[end]

The errors I get (for both examples) are:

ERROR: Failed attempt to index JuMPArray along dimension 1: 3 ∉ 0:2
 in error at error.jl:21

(By the way, is it normal this error does not show where it was triggered from my code?)

[joehuchette]

Sorry for the slow reply. Unfortunately I don't think there's much we can do here: the compiler rewrites x[end] to something like x[size(x,1)]. Are you sure this worked on v0.11?

What do you mean by "this error does not show"? This might be a bug, either on our end or with julia, depending on the behavior.

[mlubin]

@joehuchette, I think it uses the endof method, may we shouldn't define it?

[mlubin]

The current behavior is dangerous:

julia> @variable(m, x[2:4]);

julia> x[end]
x[3]

[joehuchette]

I'm fine with that

[mlubin]

I wonder if we can return a special object from endof analogous to Colon()

[mlubin]

No, that doesn't work because that would break end-1

[dourouc05]

@joehuchette: to be precise, I tried a larger piece of code that used to work with JuMP 0.11, and it was broken when I retried with JuMP 0.12.

[mlubin]

end on multidimensional arrays uses size(), so it's impossible for us to fix this

[mlubin]

Maybe the solution is to define size as an error and implement JuMP.size if you actually want to access the dimensions?