For example, you can't write c![(b, a), for &(a, b) in &[(0, 1), (2, 3)] - the macro asks for a ident rather than pat.

The equivalent of Python's {x for x in iter}.

Consider supporting an arbitrary number of for expressions rather than requiring the macro to be extended for each one? This would likely resolve #4, and lead to a fix for #6, and maybe support any number of if expressions as well? A "0-or-more" style of logic would work well, and fit nicely into a recursive macro.

It would be nice to be able to write a conditional at any location in the expression, e.g. c![a + b, for a in some_vec, if a % 5 < 2, for b in 0..10]. This could work well with generators (#1) to reduce nested computations, though I'm not sure how well that would end up vectorizing if at all.

Documentation tests are not passing at the moment. Documentation need to be rewritten for doc tests to pass.

Third level nested loops are not in the current crates.io version, do you think you can publish them?

What

Implement Generator Comprehensions

Why

Support for lazy evaluation.

The arity c! is called with determines the iteration order - c![(a, b, c), for a in 0..5, for b in 0..5, for c in 0..5] is iterated differently than c![(a, b), for a in 0..5, for b in 0..5].