VHDL integer to integer multiplication

  -- Id: A.15
  function "*" (L, R: UNSIGNED) return UNSIGNED;
  -- Result subtype: UNSIGNED((L'LENGTH+R'LENGTH-1) downto 0).
  -- Result: Performs the multiplication operation on two UNSIGNED vectors
  --         that may possibly be of different lengths.

  -- Id: A.16
  function "*" (L, R: SIGNED) return SIGNED;
  -- Result subtype: SIGNED((L'LENGTH+R'LENGTH-1) downto 0)
  -- Result: Multiplies two SIGNED vectors that may possibly be of
  --         different lengths.

  -- Id: A.17
  function "*" (L: UNSIGNED; R: NATURAL) return UNSIGNED;
  -- Result subtype: UNSIGNED((L'LENGTH+L'LENGTH-1) downto 0).
  -- Result: Multiplies an UNSIGNED vector, L, with a non-negative
  --         INTEGER, R. R is converted to an UNSIGNED vector of
  --         SIZE L'LENGTH before multiplication.

  -- Id: A.18
  function "*" (L: NATURAL; R: UNSIGNED) return UNSIGNED;
  -- Result subtype: UNSIGNED((R'LENGTH+R'LENGTH-1) downto 0).
  -- Result: Multiplies an UNSIGNED vector, R, with a non-negative
  --         INTEGER, L. L is converted to an UNSIGNED vector of
  --         SIZE R'LENGTH before multiplication.

  -- Id: A.19
  function "*" (L: SIGNED; R: INTEGER) return SIGNED;
  -- Result subtype: SIGNED((L'LENGTH+L'LENGTH-1) downto 0)
  -- Result: Multiplies a SIGNED vector, L, with an INTEGER, R. R is
  --         converted to a SIGNED vector of SIZE L'LENGTH before
  --         multiplication.

  -- Id: A.20
  function "*" (L: INTEGER; R: SIGNED) return SIGNED;
  -- Result subtype: SIGNED((R'LENGTH+R'LENGTH-1) downto 0)
  -- Result: Multiplies a SIGNED vector, R, with an INTEGER, L. L is
  --         converted to a SIGNED vector of SIZE R'LENGTH before
  --         multiplication.

signal x,y,z : integer ;
z <= x * y ;