From 8905f914a0a2174f4984564dd857d49ada87cda4 Mon Sep 17 00:00:00 2001 From: Ramakrishnan Muthukrishnan <vu3rdd@gmail.com> Date: Mon, 20 Sep 2010 22:20:40 +0530 Subject: [PATCH] code in the messaging passing section --- src/sicp/ch2_4.rkt | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/src/sicp/ch2_4.rkt b/src/sicp/ch2_4.rkt index ed348fd..4f14ab5 100644 --- a/src/sicp/ch2_4.rkt +++ b/src/sicp/ch2_4.rkt @@ -103,4 +103,16 @@ (define (make-from-mag-ang r a) (make-from-mag-ang-polar r a)) -;;; data directed programming +;;; message passing +(define (make-from-real-imag x y) + (define (dispatch op) + (cond + [(eq? op 'real-part) x] + [(eq? op 'imag-part) y] + [(eq? op 'magnitude) + (sqrt (+ (square x) (square y)))] + [(eq? op 'angle) (atan y x)] + [else + (error "unknown op" op)])) + dispatch) + -- 2.45.2