Mainstream is a very context specific term. Julia is not a general purpose language, it's primarily for numeric computing. Within the domain of technical computing it's one of the most expressive languages.
I would strongly disagree with this. Julia is a general purpose language. In fact, part of the premise is that it is a numerical computing language because it doesn't special-case numerical programming. This is in stark contrast to Matlab and R, for which numerical things are extremely special-cased.
