On Sat, Jan 22, 2011 at 5:38 AM, Nevin Liber <nevin@eviloverlord.com> wrote:
On 21 January 2011 11:56, Dean Michael Berris <mikhailberis@gmail.com>wrote:
No changing arbitrary content in the string. Concatenation is a process of creating new strings.
Ultimately the underlying string should be efficient
Please describe how you are going to make this efficient, if concatenation effectively requires an allocation (once past the small string optimization) and a copy.
It is one thing to be in a garbage collected world where the cost of allocation is relatively cheap, but that world is not C++.
Correct. So this implementation pre-supposes that there is an efficient "arena" allocator, not dissimilar from Boost.Pool, or even one that allows "growing" of buffers (via a call similar to realloc), or even something akin to what Interprocess has in the form of a `managed_heap_memory`. You can then implement an optimization for concatenation if you knew that a string to be concatenated is only referred to by only one referrer/proxy, that the RHS is a temporary, and that the resulting string would only be assigned. This implies that you need to have some smarts in the implementation -- potentially having an EDSL just for string concatenation/operations. It's needless to say that Proto would be good to use in this EDSL so that you had the capability of knowing whether strings are temporaries (generated in-place from literal strings) or an lvalue. HTH -- Dean Michael Berris about.me/deanberris