On Sat, Jun 9, 2012 at 2:32 PM, David Kastrup
<address@hidden> wrote:
Hi,
the main data structure of Lua is a "table", an associative array, and a
table t has a continguous numerically addressed part from 1..#t, with
all other indices going through a hashing mechanism. One principal
distinguishing feature, like with a Scheme hashtable, is the ability to
grow on-demand.
Scheme/Guile vectors are fixed size. Now I have a situation where I
have a basic type lattice with records stored in vectors, and this type
lattice may be extended dynamically (which typically happens at the
start of a whole file, for potentially multi-file runs). Scheme does
not offer a suitable data structure for that. It is a bit of a nuisance
that one can grow a hashtable efficiently and on-demand, but not so an
array.
Now it would be possible when the type lattice gets extended to store
the new entries in a hashtable and go from there. Or put them into a
list, and reallocate on first access beyond the existing element. That
seems rather contorted. And since there is, if I remember, a project to
run Lua on top of Guile, having a fundamental and reasonably efficient
data structure corresponding to a Lua table, or at least the contiguous
part of a Lua table, would seem like a reasonably useful idea. After
all, there already _is_ such a mechanism underlying hash tables so it
seems somewhat peculiar not to have it available for vectors as well.
Suggestions?
--
David Kastrup