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Change to use cond

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This commit is contained in:
Isaac Shoebottom 2025-03-19 15:24:15 -03:00
parent 64281e9a42
commit 31b6f1a494
1 changed files with 6 additions and 6 deletions
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12
Labs/07.rkt
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@ -4,8 +4,6 @@
(define-syntax-rule (test/exn expr msg)
(check-exn exn:fail? (lambda () expr) msg))
(define-type Node (Symbol -> (U (U Number Node) Zero)))
(define (msg0 [obj : Node] [selector : Symbol]) (obj selector))
(define (node [v : Number] [l : Node] [r : Node]) : Node
@ -17,12 +15,14 @@
[(sum) (+ v (+ (msg-num l 'sum) (msg-num r 'sum)))]
[else (error 'node (symbol->string m))])))
(define (mt) : Node
(define (mt)
(lambda ([m : Symbol])
(case m
[(sum) 0]
[else (error 'mt (symbol->string m))])))
(define-type Node (Symbol -> (U (U Number Node) Zero)))
(define (msg-num [obj : Node] [selector : Symbol]) : Number
(define result (msg0 obj selector))
(cond
@ -31,9 +31,9 @@
(define (msg-node [obj : Node] [selector : Symbol]) : Node
(define result (msg0 obj selector))
(if (not (number? result))
result
(error 'msg-node "Expected a node message")))
(cond
[(not (number? result)) result]
[else (error 'msg-node "Expected a node message")]))
(module+ test
(define tree1 (node 1 (mt) (mt)))