I somewhat wish they had used something like the ruby style for this to allow chaining of the blocks e.g.

    5.times{|x| x}.select{|x| x < 3}.collect{|x| x + 2}

Edit: Ok ignore that it seems they do have that (https://mail.mozilla.org/pipermail/rust-dev/2012-July/002000...) not sure of the difference, maybe just a result of the fast development.