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Principles of Programming Languages 2015.09.10 Notes • NAME: __________________________________ • Did you present a small project? YES / NO • Total available time: 1h 30’. • Y ou may use any written material you need. • Y ou cannot use computers or phones during the exam. 1 Scheme Consider the following procedure: (define (re-map f L cond?) (let loop ((res ’()) (cur L)) (if (null? cur) res (let* ((k #f) (v (call/cc (lambda (cont) (set! k cont) (f (car cur)))))) (if (cond? v) (cons k v) (loop (append res (list v)) (cdr cur))))))) 1.1 Description (5 points) Give a brief explanation of what re-map does, providing also a simple but meaningful example of its use and return value, different from the one of the next question. 1.2 Example usage (5 points) Let us consider to use re-map at the REPL with the following command: > (define V (re-map (lambda (x) (+ x 1)) ’(0 1 -4 3 -6 5) negative?)) Give a sequence of related commands such that the result of the last command is the list (1 2 3 4 5 6) . 1 2 Haskell 2.1 Class definition (3 points) Define a class called Blup, for a generic type T having two parameters x and y, providing two operations called f isto and f osto. f isto takes a value belonging to T and returns a value of type M aybe x, while f osto takes a value belonging to T and returns a value of type M aybe y. 2.2 Instance I (4 points) Define the sum type Blargh with two parameters of types a and b. It has three data constructor: either Bip with two parameters of types respectively a and b, or Bop with only one parameter of type a, or Bup with no parameters. Make Blargh an instance of class Blup, where f isto is used to access to data of type a, and f osto to data of type b. 2.3 Instance II (4 points) Define the sum type Blarf with two parameters of types a and b. It has…