alternative to check, whether a value is in a set

Question

Hi All,

I have the following code. It looks ugly, if the value equals to one of the following value then do something.

var
  Value: Word;
begin
  Value := 30000;
  if (Value = 30000) or (Value = 40000) or (Value = 1) then
    do_something;
end;

I want to refactor the code as follows:

var
  Value: Word;
begin
  Value := 30000;
  if (Value in [1, 30000, 40000]) then // Does not work
    do_something;
end;

However, the refactored code does not work. I assume that a valid set in Delphi accepts only elements with type byte. If there any good alternative to refactor my original code (besides using case)?

Answer 1

I think something like this?

case value of
  1, 30000, 40000: do_somthing
end;

Answer 2

Not as succint as Roald's answer, but if you are set on using sets, you could do:

var
  Value: Word;
  IntegerSet: TIntegerSet;
begin
  Include(IntegerSet, 1);
  Include(IntegerSet, 30000);
  Include(IntegerSet, 40000);
  Value := 30000;
  if (Value in IntegerSet) then
    DoSomething;
end;

The Include's are of course a hinderance, but could have been set elsewhere (making them reusable):

procedure CheckAndDo(const aValue: Integer; const aCheckAgainst: TIntegerSet);
begin
  if (aValue in aCheckAgainst) then
    DoSomethingComplicated;
end;

procedure DoIt;
var
  CheckValues: TIntegerSet;
begin
  Include(CheckValues, 1);
  Include(CheckValues, 30000);
  Include(CheckValues, 40000);
  //...
  CheckAndDo(30000, CheckValues);
end;

Answer 3

How about using an open array?

function ValueIn(Value: Integer; const Values: array of Integer): Boolean;
var
  I: Integer;
begin
  Result := False;
  for I := Low(Values) to High(Values) do
    if Value = Values[I] then
    begin
      Result := True;
      Break;
    end;
end;

Example (pseudo-code):

var
  Value: Integer;
begin
  Value := ...;
  if ValueIn(Value, [30000, 40000, 1]) then
    ...
end;

Answer 4

There is a class for larger bitsets, see Classes.TBits.

While it won't do constant expressions easily, it can be useful in certain other cases.