Hans: To simultaneously stand my ground and display my ignorance: I've written several flavors of hash tables in my life, but I'm not sure how the Stroustrup code sample helps in this case. If you are suggesting that I hack the Chuck source code, you should know that I do entertain such ideas from time to time, but I usually come back to my senses within 25::samp -- it's just not on my list of priorities. A "written entirely in ChucK" solution -- albeit non-optimal in execution speed -- is good enough for my needs. I'm more into optimizing my days than my milliseconds. Thanks, though. - Rob On 30 Sep 2009, at 14:01, Hans Aberg wrote:

On 30 Sep 2009, at 22:12, Robert Poor wrote:

...

To clarify: I'd like to implement a set for storing a collection of homogenous objects. Specifically, I need to be able to test for the presence of an object in the set, add an object to the set (if not already present), delete a object from the set, and iterate over all the objects in the set. This last requirements, sadly, eliminates Chuck's "associative arrays".

It's worth pointing out that:

arbitraryobject.toString()

will generate a string of the form "ClassName:hexLocation". Assuming that Chuck NEVER (ever) relocates a live object in memory (Chuck has a reference counting GC, not a copying GC, true?), that string could be useful as a unique ID. But Chuck lacks the string operations to reduce a string into a hash key.

Bjarne Stroustrup, "The C++ Programming Language", 3.1.3, has a simple hash function: name* look(const char* p, int ins=0); name* insert(const char* s) { look(s, 1); }

struct name { char* string; name* next; double value; }

const TBLSZ = 23; name* table[TBLSZ];

name* look(const char* p, int ins=0) { int ii = 0; const char* pp = p; while (*pp) ii = ii<<1 ^ *pp++; // Hash function using eor: ii<<1; ii ^= *pp++;

if (ii < 0) ii = -ii; // Reduce to array range. ii %= TBLSZ;

for (name* n = table[ii]; n; n = n->next) // Search if (strcmp(p, n->string) == 0) return n;

if (ins == 0) error("name not found");

name* nn = new name; // Insert nn->string = new char[strlen(p) + 1]; strcpy(nn->string, p); nn->value = 1; nn->next = table[ii]; table[ii] = nn; return nn; }

Hans