Updated again.

2025-10-10 01:10:31 -04:00
parent 3fb80bd5e0
commit 15e68d2dcc
1 changed files with 3 additions and 1 deletions
@@ -21,13 +21,15 @@
 ; Tree t -> Bool
 ; Determines whether a Tree is a binary search tree.
 (define (bst? t)
-  (local [; Convenient form of greater than.
+  (local [; <2: U{Num, Sym}, Num, U{Num, Sym} → Bool
+          ; Convenient form of greater than. Slightly hack.
          (define (<2 a b c)
            (cond [(and (symbol? a) (symbol? c)) #t]
                  [(symbol? a) (< (- b 1) b c)]
                  [(symbol? c) (< a b (+ b 1))]
                  [else (< a b c)]))

+          ; recurse: t: Tree, lower: Num, upper: Num → Bool
          ; Recursively checks left & right with lower & upper bounds.
          (define (recurse t lower upper)
            (cond [(symbol? t) (symbol=? t 'end)]