> if (err) return callback(err) > That line is haunting me in my dreams now. What happened to the DRY principle? iferr = (succfn, errfn) -> (err, a...) ->

> if (err) return callback(err) > That line is haunting me in my dreams now. What happened to the DRY principle? iferr = (succfn, errfn) -> (err, a...) -> if err? then errfn err else succfn a... show_user = (id, cb) -> db.query ..., iferr cb, (user) -> ... FTFY, no promises needed. (not to say that promises don't have other advantages, but that specific complaint is easily fixable with an higher-order function to abstract it away) (JavaScript version: http://coffeescript.org/#try:%20%20iferr%20%3D%20(succfn%2C%20errfn)%20-%3E%20(err%2C%20a...)%20-%3E%0A%20%20%20%20if%20err%3F%20then%20errfn%20err%20else%20succfn%20a...%0A%0A%20%20show_user%20%3D%20(id%2C%20cb)%20-%3E%0A%20%20%20%20db.query%20foo%2C%20iferr%20cb%2C%20(user)%20-%3E%0A%20%20%20%20%20%20bar http://coffeescript.org/#try:%20%20iferr%20%3D%20(succfn%2C%...)