Bitmap/Midpoint circle algorithm: Difference between revisions

=={{header|Common Lisp}}==

Based upon the OCaml version.

<pre>(defun draw-circle (draw-function x0 y0 radius)

(labels ((foo (x y)

(funcall draw-function x y))

(put (x y m)

(let ((x+ (+ x0 x))

(x- (- x0 x))

(y+ (+ y0 y))

(y- (- y0 y))

(x0y+ (+ x0 y))

(x0y- (- x0 y))

(xy0+ (+ y0 x))

(xy0- (- y0 x)))

(foo x+ y+)

(foo x+ y-)

(foo x- y+)

(foo x- y-)

(foo x0y+ xy0+)

(foo x0y+ xy0-)

(foo x0y- xy0+)

(foo x0y- xy0-)

(multiple-value-bind (y m) (if (plusp m)

(values (1- y) (- m (* 8 y)))

(values y m))

(when (<= x y)

(put (1+ x)

y

(+ m 4 (* 8 x))))))))

(put 0 radius (- 5 (* 4 radius)))

(values)))</pre>

<pre>CL-USER> (let ((buffer (make-array '(30 30)

:element-type 'bit)))

(draw-circle (lambda (x y)

(setf (bit buffer x y) 1)) 15 15 10)

buffer)

;; edited for your convenience

(( )

( 1 1 1 1 1 1 1 )

( 1 1 1 1 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 )

( 1 1 1 1 1 1 )

( 1 1 1 1 1 1 1 )

( ))

</pre>