On Monday, 14 May 2012 at 16:30:21 UTC, deadalnix wrote:
Le 14/05/2012 17:00, Roman D. Boiko a écrit :
Making it a class would give several benefits:
* allow not to worry about allocating a big array of tokens.
E.g., on
64-bit OS the largest module in Phobos (IIRC, the
std.datetime) consumes
13.5MB in an array of almost 500K tokens. It would require 4
times
smaller chunk of contiguous memory if it was an array of class
objects,
because each would consume only 8 bytes instead of 32.
Why is this a benefice ?
NNTP error: 400 load at 23.60, try later prevented me from
answering :)
Because it might be difficult to find a big chunk of available
memory (3.5M vs 14M for this particular case).
* allow subclassing, for example, for storing strongly typed
literal
values; this flexibility could also facilitate future
extensibility (but
it's difficult to predict which kind of extension may be
needed)
I'm pretty sure that D's token will not change that much. If
the need isn't identified right know, I'd advocate for YAGNI.
Agree.
* there would be no need to copy data from tokens into AST,
passing an
object would be enough (again, copy 8 instead of 32 bytes);
the same
applies to passing into methods - no need to pass by ref to
minimise
overhead
Yes but now you add pressure on the GC and add indirections.
I'm not sure it worth it. It seems to me like a premature
optimization.
It looks so. Thanks.
It would incur some additional memory overhead (at least 8
bytes per
token), but that's hardly significant. Also there is
additional price
for accessing token members because of indirection, and,
possibly, worse
cache friendliness (token instances may be allocated anywhere
in memory,
not close to each other).
These considerations are mostly about performance. I think
there is also
some impact on design, but couldn't find anything significant
(given
that currently I see a token as merely a datastructure without
associated behavior).
Could anybody suggest other pros and cons? Which option would
you choose?
You are over engineering the whole stuff.
I'm trying to solve this and other tradeoffs. I'd like to
simplify but satisfy my design goals.
