I think it wold be nice if users could define their own dot vectorized operators, some examples are in (.in/.∈), and is (.is / .===). This is the more julian thing to do IMHO (think of identifiers with a bang also foo!), this would also allow us to use this functions as infix operators, similar to the now vast array of symbols that we can choose from as infix operators for user defined purposes.

Refs:

• Element-wise in operator #5212
• Support non-vectorized syntax in @where JuliaData/DataFramesMeta.jl#39

This would be an easy solution for the user needs (see DataFramesMeta suggestion to use a macro within a macro and change non dot operator semantics, when a function would be enough) without having to implement such methods in Base, selectively add (and debate) such operators for just a few of them (most would never make it into Base), instead this proposal would generalize dot vectorized operators into a common julian thing to do.

cc @JeffBezanson @StefanKarpinski @nalimilan