That example is using “logical vectors”, which you’d come across in more data-science languages like Matlab, Octave, R, etc. Julia[1] has a more modern take on

That example is using “logical vectors”, which you’d come across in more data-science languages like Matlab, Octave, R, etc. Julia[1] has a more modern take on y==1, by having explicit syntax for element-wise operations, so it uses y.==1 instead. What I’m really saying is that there’s quite a bit of precedent for that syntax, but it comes from a more specialised field so it is easy to have not come across it before. [1] https://docs.julialang.org/en/v1/manual/functions/#man-vectorized https://docs.julialang.org/en/v1/manual/functions/#man-vecto...