Issue #20664 has been updated by Eregon (Benoit Daloze). One issue with `take_until` is: does it include the element for which it yielded `true`? In the description example `Enumerator.produce(3, until: :zero?, &:pred)` the result does include `0`. But for `Enumerator.produce(parent, &:parent_directory).take_until(&:nil?)` the intention is to not include `nil` in the result. Maybe we should have 2 variants of `take_until`, or a keyword argument whether to include the last element or not. IMO `before:/until:` kwargs for `Enumerator.produce` feel too ad-hoc. `take_until` is something I wished existed already. But we need to address whether it includes the last element or not. ---------------------------------------- Feature #20664: Add `before` and `until` options to Enumerator.produce https://bugs.ruby-lang.org/issues/20664#change-109531 * Author: knu (Akinori MUSHA) * Status: Open ---------------------------------------- Enumerator.produce provides a nice way to generate an infinite sequence but is a bit awkward to define how to end a sequence. It lacks a simple and easy way to produce typical finite sequences in an intuitive syntax. This proposal attempts to solve the problem by adding these two options to the method: - `before`: when provided, it is used as a predicate to determine if an iteration should end before a generated value gets yielded. - `until`: when provided, it is used as a predicate to determine if an iteration should end until after a generated value gets yielded. Any value that responds to `to_proc` and returns a `Proc` object is accepted in these options. A typical use case for the `before` option is traversing a tree structure to iterate over the ancestors or following/preceding siblings of a node. The `until` option can be used when there is a clear definition of the "last" value to yield. ```ruby enum = Enumerator.produce(File, before: :nil?, &:superclass) enum.to_a #=> [File, IO, Object, BasicObject] enum = Enumerator.produce(3, until: :zero?, &:pred) enum_to_a #=> [3, 2, 1, 0] ``` ---Files-------------------------------- 0001-Add-before-and-until-options-to-Enumerator.produce.patch (10.7 KB) -- https://bugs.ruby-lang.org/