A highly parameterized program is easier to write and maintain than many specialized versions for different applications, but may be inefficient.

Example: Draw a line: (x₁, y₁) to (x₂, y₂).
Options include:

• Width of line (usually 1)

• Color

• Style (solid, dashed, etc.)

• Ends (square, beveled)

If all of these options are expressed as parameters, it makes code longer, makes calling sequences longer, and requires interpretation at runtime. Partial evaluation can produce efficient specialized versions automatically.

(draw-line x y (+ x 100) y 1 'black 'solid)

Contents    Page-10    Prev    Next    Page+10    Index