Skip 2.74. And 2.75 is finished.

Author: xudon9

2.75.scm

@@ -0,0 +1,22 @@
+(define (apply-generic op arg) (arg op))
+
+(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: 
+                    MAKE-FROM-REAL-IMAG" op))))
+  dispatch)
+
+(define (make-from-mag-ang r a)
+  (define (dispatch op)
+    (cond ((eq? op 'real-part) (* r (cos a)))
+          ((eq? op 'imag-part) (* r (sin a)))
+          ((eq? op 'magnitude) r)
+          ((eq? op 'angle) a)
+          (else (error "Unknown op: MAKE-FROM-REAL-IMAG" op))))
+  dispatch)