Contributed by Michel Dagenais (dagenais@vlsi.polymtl.ca), 1994.

INTERFACE RealTransform;

Here is the layout of the elements of our matrix. A number is the corresponding index into the array, `x' means the element is not held explicitly.

            Column
           0   1   2
         +---+---+---+
        0| 0 | 1 | x |
      R  +---+---+---+
      o 1| 2 | 3 | x |
      w  +---+---+---+
        2| 4 | 5 | x |
         +---+---+---+

IMPORT RealPoint;

TYPE T = ARRAY [0 .. 5] OF REAL;

CONST
  Identity = T{1.0, 0.0,        (* 0.0 *)
               0.0, 1.0,        (* 0.0 *)
               0.0, 0.0};       (* 1.0 *)

PROCEDURE Scale(READONLY sx, sy: REAL): T;
PROCEDURE Translate(READONLY tx, ty: REAL): T;
PROCEDURE Rotate(READONLY radians: REAL): T;

PROCEDURE Concat(READONLY m, n: T): T;
PROCEDURE Concat3(READONLY l, m, n: T): T;

PROCEDURE Inverse (READONLY m: T): T;

PROCEDURE Transform(READONLY m: T; READONLY p: RealPoint.T): RealPoint.T;

END RealTransform.