Functional forms and argument ordering

[tshort]

Many of the LINQ-like operations have a functional form where a function is passed as an argument, like:

where(g, d -> mean(d[:a]) > 0)

This form is quite common with LINQ libraries. The issue is argument ordering. Base Julia functions like map all have the function passed as the first argument. The LINQ standard uses the function as the second argument, and passing the "operations" as the second argument is more consistent with the macro form: @where(g, mean(:a) > 0).

Our choices are: (1) follow Julia base, (2) follow the LINQ standard, or (3) define both.