It took me a while to figure out why it was erroring Given this piece of a script
@show(sampr1, sampr2) @show(typeof(sampr1), typeof(sampr2)) @show(@sprintf("-T%d/%d/1", sampr1[1], sampr2[1])) it error ed with an incomprehensible error sampr1 = [-1167.0] sampr2 = [1169.0] typeof(sampr1) = Array{Float64,2} typeof(sampr2) = Array{Float64,2} @sprintf("-T%d/%d/1",sampr1[1],sampr2[1]) = "-T-1167/1169/1" ERROR: TypeError: non-boolean (Array{Bool,2}) used in boolean context [inlined code] from show.jl:127 it turned out that it wanted @show(@sprintf("-T%d/%d/1", sampr1[1,1], sampr2[1,1])) but the sampr1 & sampr2 are the result of a previous computation so not at all obvious of what was going on. Specially because accessing sampr1[1] is a perfectly valid statement julia> sampr1 = zeros(1,1); 1x1 Array{Float64,2}: 0.0 julia> sampr1[1] 0.0