pre-generic dictionary class
I think that some functionality in GExperts (and some of my other tools) could profit from switching from sorted TStringLists to a dictionary. Unfortunately I can't just use TDictionary<string, [whatever]> because I want to continue supporting Delphi versions that didn't have generics (in particular Delphi 2007). Does anybody know of a free dictionary implementation that stores pointers indexed by strings? I know of THashedStringList but it has too many gotchas to simply use it (e.g. the hashes get recalculated every time a new item was inserted and IndexOf is called, which is exactly what I would need to do). Yes, I could write one myself, but why reinvent the wheel if there already is one?
I have never liked the idea of a hash, and I use an implementation of a ternary seach tree as a dictionary. I based it on an article in Dr Dobb's Journal in 1998, and it has stood the test of time!
I have versions for C and Pascal; the latter for AnsiChar, WidwChar 32-bit and WideChar 64-bit keys. It is incredibly fast and easy to use, and has reasonable memory consumption, unless of course you load a million random 100-byte keys (which takes only a second or so). It has various ways to load and look up keys, and to traverse the set; values can be integer, object or string. I use it it in many different ways, both to match a full key and to find the longest initial partial key. On updating a value, the space used by the old value is not recovered, but that suits most of my uses as a dictionary; and the unit does include a function to rebuild the data store for a dynamic application, if you can spare a second to do so. In its simplest form:
tree := tTSTtree.Create;
tree.insert(key, value);
q := tree.match(key);
if (q <> nil) then s := string(pchar(q));
The source is reasonably well commented, and I would be happy let you have a copy, but I have never got around to properly documenting it and uploading it somewhere.
tree.insert(key, value);
q := tree.match(key);
if (q <> nil) then s := string(pchar(q));
The source is reasonably well commented, and I would be happy let you have a copy, but I have never got around to properly documenting it and uploading it somewhere.
