How do I pass a range as a parameter in Delphi?

In Delphi, I can define a range of characters or integ开发者_如何转开发ers as demonstrated below:

var
  a,i: integer;
  b: char;
  intrange: 1..9;
  charrange: 'α' .. 'ζ';

begin

  for a := low(IntRange) to high(IntRange) do
  begin
    Memo1.Lines.Add('Integer Range Iteration = ' + intToStr(a) ) ;
  end;

  i:=0;
  for b := low(charrange) to high(charrange) do
  begin
    i := i + 1;
    Memo1.Lines.Add('Character Range Iteration = ' + intToStr(i) + ',   value = ' + b +'  ord '+ inttostr(ord(b))) ;
  end;
end;

How can I pass a range as a parameter to a function?

You can use subrange types:

type
  TCharrange = 'α' .. 'ζ';

procedure MyFunction(Char: TCharrange);

Now you can do

MyFunction('γ');

whereas

MyFunction('a');

won't work.

As I understand your question you want to pass a range rather than a character that is within some specified range. If that is a correct understanding then you would need to pass two parameters (min and max) or perhaps wrap them up in a record.

You can try sets in certain cases, for example:

type
  TMyRange = 1..5;
  TMyRangeSet = Set of TMyRange;

procedure A(const V: TMyRangeSet);
var X : TMyRange;
begin
  for X := Low(TMyRange) to High(TMyRange) do
    if X in V then { included } 
end;

begin
  A([3..4]);
end.

I beleive you'd need to define it as a type first, something like:

type
  TMyRange = 1..2;

then:

function Whatver(Range: TMyRange): Boolean;
begin

end;

I am rather new to generics, but I think that this might be a rather neat solution to the second interpretation (the David Heffernan interpretation) of your problem.

type
  TRange<T> = record
    MinVal: T;
    MaxVal: T;
    constructor Create(AMinVal, AMaxVal: T);
  end;

  TCharrange = TRange<Char>;
  // TIntrange = TRange<Integer>;
  // etc.

constructor TRange<T>.Create(AMinVal, AMaxVal: T);
begin
  MinVal := AMinVal;
  MaxVal := AMaxVal;
end;

Now you can do

procedure MyFunction(Char: TCharrange);
begin
  ShowMessage(Char.MinVal);
  ShowMessage(Char.MaxVal);      
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  r: TCharrange;
begin
  r.Create('a', 'c');
  MyFunction(r);
end;