Darren Duncan wrote: > pugs-comm...@feather.perl6.nl wrote: >> >> Log: >> [S02] clarify that Pairs and Mappings are mutable in value, but not in key > > <snip> >> >> KeyHash Perl hash that autodeletes values matching default >> KeySet KeyHash of Bool (does Set in list/array context) >> KeyBag KeyHash of UInt (does Bag in list/array context) >> + Pair A single key-to-value association >> + Mapping Set of Pairs with no duplicate keys > > <snip> >> >> +As with C<Hash> types, C<Pair> and C<Mapping> are mutable in their >> +values but not in their keys. (A key can be a reference to a mutable >> +object, but cannot change its C<.WHICH> identity. In contrast, >> +the value may be rebound to a different object, just as a hash >> +element may.) > > Following this change, it looks to me like Mapping is exactly the same as > Hash. So under what circumstances should one now choose whether they want > to use a Hash or a Mapping? How do they still differ? -- Darren Duncan
I don't think they do. IMHO, Mapping should definitely be immutable in both key and value; it is to Hash as Seq is to Array. (Side note: why is List considered to be immutable? Doesn't it change whenever its iterator is read?) The question in my mind has to do with Pair: if Pair is being redefined as mutable in value, should it have an immutable counterpart? If so, what should said counterpart be called? -- Jonathan "Dataweaver" Lang
