std.algorithm.remove and principle of least astonishment

[Rainer Deyke]

On 11/19/2010 16:40, Andrei Alexandrescu wrote:
> On 11/19/10 12:59 PM, Bruno Medeiros wrote:
>> Sorry, what I mean is: so we agree that char[] and wchar[] are special.
>> Unlike *all other arrays*, there are restrictions to what you can assign
>> to each element of the array. So conceptually they are not arrays, but
>> in the type system they are very much arrays. (or described
>> alternatively: implemented with arrays).
>>
>> Isn't this a clear sign that what currently is char[] and wchar[] (=
>> UTF-8 and UTF-16 encoded strings) should not be arrays, but instead a
>> struct which would correctly represents the semantics and contracts of
>> char[] and wchar[]? Let me clarify what I'm suggesting:
>> * char[] and wchar[] would be just arrays of char's and wchar's,
>> completely orthogonal with other arrays types, no restrictions on
>> assignment, no further contracts.
>> * UTF-8 and UTF-16 encoded strings would have their own struct-based
>> type, lets called them string and wstring, which would likely use char[]
>> and wchar[] as the contents (but these fields would be internal), and
>> have whatever methods be appropriate, including opIndex.
>> * string literals would be of type string and wstring, not char[] and
>> wchar[].
>> * for consistency, probably this would be true for UTF-32 as well: we
>> would have a dstring, with dchar[] as the contents.
>>
>> Problem solved. You're welcome. (as John Hodgeman would say)
>>
>> No?
> 
> I don't think that would mark an improvement.

You don't see the advantage of generic types behaving in a generic
manner?  Do you know how much pain std::vector<bool> caused in C++?

I asked this before, but I received no answer.  Let me ask it again.
Imagine a container Vector!T that uses T[] internally.  Then consider
Vector!char.  What would be its correct element type?  What would be its
correct behavior during iteration?  What would be its correct response
when asked to return its length?  Assuming you come up with a coherent
set of semantics for Vector!char, how would you implement it?  Do you
see how easy it would be to implement it incorrectly?


-- 
Rainer Deyke - rainerd at eldwood.com