clang 3.6 fold expression left/right

Question

I\'m trying the fold expression with clang 3.6 \'--std=c++1z\', but something I don\'t quite get. The function that I\'m testing is:

auto minus = [](auto...          


        

Answer 1

n4191 was revised by n4295. According to that, an expression of the form (e op ...) is a unary right fold, and that is expanded as: E1 op (... op (EN-1 op EN)), i.e. as a right fold expansion.

This does seem to be the reverse of what n4191 stated in terms of the fold direction. Clang 3.6 implements the n4295 proposal, as shown here.

... - args would be a unary left fold and expand in the direction you want.