Sorry José, I was wrong when i wrote > If we support improper lists, prefix could be any term, not just a list.
what meant is that if we support List.ends_with?/2, then suffix could be any term (but I will show that this is still wrong) List.ends_with?([1, 2 | 3], 3) #=> true but that could be ambiguous, List.ends_with?([1, 2, 3], [2, 3]) #=> true List.ends_with?([1 | [2, 3]], [2, 3]) #=> true So suffix could ONLY be a list or an improper list. List.ends_with?([1, 2 | 3]], [2 | 3]) #=> true List.ends_with?([1, 2 | 3]], [2 | 3]) #=> true Regarding prefixes. We could still support improper lists as the first argument, List.starts_with?([1, 2 | 3], [1, 2]) #=> true and improper lists as the prefix (returns true only if both lists are the same) List.starts_with?([1, 2 | 3], [1, 2 | 3]) #=> true So wrapping up, lists, prefixes and suffixes could be all maybe_improper_list On Tue, 21 Feb 2017 16:02:58 +0100 José Valim <jose.va...@plataformatec.com.br> wrote: > Excellent questions! > > I don't think we should support improper lists because there is no notion > of prefix for improper list. For instance, I would not expect this to match: > > List.starts_with?([1, 2], [1 | 2]) > > > Because we would compare 1 == 1 and then [2] to 2. The only situation they > would match is if they are exactly equal and then the function is no longer > necessary. > > > *José Valim* > www.plataformatec.com.br > Skype: jv.ptec > Founder and Director of R&D > > On Tue, Feb 21, 2017 at 3:38 PM, eksperimental <eksperimen...@autistici.org> > wrote: > > > Hi, List.starts_with?/2 have recently been introduced > > https://github.com/elixir-lang/elixir/pull/5789 > > > > I was working on improving the specs and the code, > > and I have realized there are a few issues I would to work on. > > > > Initially would like to to know whether we should support improper lists, > > that would determine how > > the code can be optimized. > > > > I would say yes, we should support improper lists. > > But we also need to keep in mind that we will probably will end up adding > > List.ends_with?/2 too, > > so we need to keep that in mind > > > > If we support improper lists, prefix could be any term, not just a list. > > > > -- > > You received this message because you are subscribed to the Google Groups > > "elixir-lang-core" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to elixir-lang-core+unsubscr...@googlegroups.com. > > To view this discussion on the web visit https://groups.google.com/d/ms > > gid/elixir-lang-core/20170221213857.6c3a8f4f.eksperimental%40autistici.org > > . > > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/20170222010356.6eaf2436.eksperimental%40autistici.org. For more options, visit https://groups.google.com/d/optout.
