Talk:Lucas number

Q: Why not use UInt64 as return type for the function. It should be the same on all platforms.

Remark: it seems a bit strange to me to derive Lucas(n) from Fib(n), because the Fibonacci sequence is jus a special case of the Lucas numbers (with starting values 1,1). --Bart (talk) 19:15, 10 November 2018 (CET)

Here's an example of what I mean:

{
A more general form of the Lucas series, where the 2 starting values
can be set using parameters
}
function LucasGen(L1, L2, N: UInt64): UInt64;
var
  i, LucMin1, LucMin2: UInt64;
begin
  if (N = 0) then
    Raise ERangeError.Create('Lucas function is undefined for 0.');
  if (N = 1) then
    Exit(L1)
  else if (N = 2) then
    Exit(L2)
  else
  begin
    LucMin1 := L2;
    LucMin2 := L1;
    i := 2;
    while (i <> N) do
    begin
      Inc(i);
      Result := LucMin2 + LucMin1;
      LucMin2 := LucMin1;
      LucMin1 := Result;
    end;
  end;
end;

function Lucas(N: UInt64): UInt64;
begin
  Result := LucasGen(2,1,N);
end;


function Fib(N: UInt64): UInt64;
begin
  Result := LucasGen(1,1,N);
end;

--Bart (talk) 19:25, 10 November 2018 (CET)