Logo

‹procedure-definition›	::=	to ‹identifier› ‹parameter›* ‹statement›* end
‹procedure-call›	::=	‹identifier› ‹arg-expr›
‹parameter›	::=	an identifier prefixed with :

‹expression›	::=	numeric literal
	\|	‹parameter›
	\|	‹expression› ‹operator› ‹expression›
‹operator›	::=	+ \| - \| * \| / \| = \| < \| >

syntax
(forward d)
syntax
(fd d)

Move forward d units.

syntax
(backward d)
syntax
(bk d)

Move backward d units.

syntax
(left φ)

Turn left (anticlockwise) φ degrees.

syntax
(right φ)

Turn right (clockwise) φ degrees.

syntax
(penup)
syntax
(pu)

Raise the turtle’s pen so that lines are not drawn when moving.

syntax
(pendown)
syntax
(pd)

Lower the turtle’s pen to draw lines.

syntax
(home)

Return to the origin in a straight line.

syntax
(clearscreen)
syntax
(cs)

Clear the screen.

The file sierpinski.rkt in this package shows how to draw a Sierpinski triangle using turtle graphics.