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
