Re: [DUG]: Friday Challange

Thu, 31 Oct 2002 13:48:48 -0800

Just as an aside, could u tell me why u are all using pred(itemcount) instead of (itemcount - 1)????
 
 
----- Original Message -----
Sent: Friday, November 01, 2002 9:38 AM
Subject: RE: [DUG]: Friday Challange

I've done this in 5 different ways.  One of the more flexible is
 
function statement(Sep, Quote: String): string;
var
  I: integer;
begin
  Result := Sep;
  for I := 0 to pred(ItemCount) do
    Result := format('%s%s%s%s%s',[Result,Sep,Quote,Item[I],Quote])
  Delete(Result, 1, Length(Sep);
end;
 
The main advantage of this is speed where the list is large - the conditional is removed from the iteration. 
(Note that many variants of SQL limit the number of parameters in a list to 255 and the length of the list to 2000 or 4000.)
 
One of our standard method for comma separated lists is to use a stringlist (not efficient but simple and avoids empty lists):
 
function statement(FieldName, EmptyCondition: String; Quote: Boolean): string;
var
  i integer;
  ResList : TStringList;
begin
  ResList := TStringList.Create;  
  for I := 0 to pred(ItemCount) do
    if Quote
      ResList.Add(Format('''%s''',[Item[i]]))
    else
      ResList.Add(Item[i]);
  if ResList.Count > 0 then
    Result := Format('%s in (%s)',[FieldName, ResList.CommaText]
  else
    Result := EmptyCondition;
  ResList.Free;
end;
 

Result := $0.02;

Stephen

-----Original Message-----
From: Neven MacEwan [mailto:[EMAIL PROTECTED]]
Sent: Friday, 1 November 2002 12:28 a.m.
To: Multiple recipients of list delphi
Subject: [DUG]: Friday Challange

Hi all,
 
Further to my enpty string question, I'm writing a lot of
functions that return a set of strings joined by a separator
ie 'col1, col2,...' or 'col1 = 'a' and colb = 'b'' (as you may guess
these are all parts of SQL Statements)
 
given a function 'Itemcount' that returns the number of items
and item(i) that returns the item string, and function sep what is the
best form of such a function
 
to seed the duscussion I'll give you one of my variants
 
function statement: string;
var
  I: integer;
begin
  Result := '';
  for I := 0 to pred(ItemCount) do
    if I = 0 then Result := Item(I)
    else Result := format('%s%s%s',[Result,Sep,Item(I)])
end;
 
Variants and explainations pls
 
Neven
 

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