1 files changed, 35 insertions, 0 deletions
diff --git a/semestr-2/racket/l11/solution.rkt b/semestr-2/racket/l11/solution.rkt
new file mode 100644
index 0000000..55e4ba6
--- /dev/null
+++ b/semestr-2/racket/l11/solution.rkt
@@ -0,0 +1,35 @@
+#lang racket
+
+(provide (contract-out
+           [with-labels with-labels/c]
+           [foldr-map foldr-map/c]
+           [pair-from pair-from/c]))
+(provide with-labels/c foldr-map/c pair-from/c)
+
+
+(define with-labels/c (parametric->/c [a b] (-> (-> a b) (listof a) (listof (cons/c b (cons/c a null?))))))
+
+(define (with-labels f xs)
+  (if (null? xs)
+      null
+      (cons (list (f (car xs)) (car xs)) (with-labels f (cdr xs)))))
+
+
+
+(define foldr-map/c (parametric->/c [x a f] (-> (-> x a (cons/c f a)) a (listof x) (cons/c (listof f) a))))
+
+(define (foldr-map f a xs)
+  (define (it a xs ys)
+    (if (null? xs)
+        (cons ys a)
+        (let [(p (f (car xs) a))]
+          (it (cdr p)
+              (cdr xs)
+              (cons (car p) ys)))))
+  (it a (reverse xs) null))
+
+
+(define pair-from/c (parametric->/c [x fx gx] (-> (-> x fx) (-> x gx) (-> x (cons/c fx gx)))))
+
+(define (pair-from f g)
+  (lambda (x) (cons (f x) (g x))))
+\ No newline at end of file