Givens rotation / Поворот Гивенса

const
  n = 2;
  eps = 1000;
var
  col, row, i, j: integer;
  r,c,s, row_i, col_i: real;
  mas: array [0..n, 0..n] of real;
  Q: array [0..n, 0..n] of real;

begin
  mas[0, 0] := 0; mas[0, 1] := -1; mas[0, 2] := 1;
  mas[1, 0] := 4; mas[1, 1] := 2; mas[1, 2] := 0;
  mas[2, 0] := 3; mas[2, 1] := 4; mas[2, 2] := 0;

  Q[0, 0] := 1; Q[0, 1] := 0; Q[0, 2] := 0;
  Q[1, 0] := 0; Q[1, 1] := 1; Q[1, 2] := 0;
  Q[2, 0] := 0; Q[2, 1] := 0; Q[2, 2] := 1;

  for col := 0 to n do
  begin
   for row := col+1 to n do
    if mas[row, col] <> 0 then
    begin
      r := sqrt(mas[col, col]*mas[col, col] + mas[row, col]*mas[row, col]);
      c := mas[col, col] / r;
      s := -mas[row, col] / r;

      for i := 0 to n do
      begin
        {R}
        col_i := mas[col, i] * c + mas[row, i] * (-s);
        row_i := mas[col, i] * s + mas[row, i] * c;
        mas[col, i] := col_i;
        mas[row, i] := row_i;
        {Q}
        col_i := Q[i, col] * c + Q[i, row] * (-s);
        row_i := Q[i, col] * s + Q[i, row] * c;
        Q[i, col] := col_i;
        Q[i, row] := row_i;
      end;
    end;
  end;

  writeln('R:');
  for i := 0 to n do
  begin
   for j := 0 to n do
    write(round(mas[i, j] * eps) / eps, Chr(9));
  writeln();
  end;

  writeln('Q:');
  for i := 0 to n do
  begin
   for j := 0 to n do
    write(round(Q[i, j] * eps) / eps, Chr(9));
  writeln();
  end;
end.