A transformation is defined by specifying two ordered sets of transformation functions which define its forward and inverse mappings. These functions are stored as character data (typically in the elements of two CHARACTER arrays) and have the general form:
variable [= expression]
where variable is a valid variable name and expression is an arithmetic expression. Transformation functions therefore resemble Fortran 77 assignment statements, except that the contents of the square brackets [...] may be omitted in appropriate circumstances (see below).
TRANSFORM Coordinate Transformation Facility