[fpc-devel] Stringlist sortstyle ssluser

[Franz Müller]

In the current implementation of TStringlist, there is a property 
SortStyle, which is somewhat similar to the property Sorted. However, it 
is different from sorted in that it allows 3 values: sslnone, which 
corresponds to sorted=false, sslAuto, which corresponds to sorted=true, 
and sslUser, which correspnds to ????

This third value introduces some inconsistency. If the user is 
responsible for sorting, as is written in the documentation, this must 
be meant to be done by caling customsort - otherwise it would make 
absolutey no sense to leave sorting to the user. And in addition the 
procedures used for comparing auto-sorted procedures are local to the 
Stringlist unit, so the application programmer would not even be able to 
use these methods for sorting himself.

The code for find looks currently ike this:

function TStringList.Find(const S: string; out Index: Integer): Boolean;
var
   L, R, I: Integer;
   CompareRes: PtrInt;
begin
   Result := false;
   Index:=-1;
   if Not Sorted then
     Raise EListError.Create(SErrFindNeedsSortedList);
   // Use binary search.
...

While adding items to such stringlists works like for TStrings (making 
the stringlist unsorted instead of "sslUser" sorttype) it is currently 
possible to use the find method  on such a stringlist directly without 
error message (And IndexOf uses binary search which won't work 
correctly). Both methods should treat such stringlists as unsorted (-> 
find not allowed, IndexOf works sequentially), as the compare functions 
used in the binary search normally will be incompatible with the sort 
order of the stringlist.

I wonder if there is any useful purpose for the value sslUser. Anyway, 
the stringlist code itself should always treat such stringlists like 
unsorted, i.e. should never use "if sorted", but always "if 
SortStyle=sslAuto".