midterm1-fall12-solutions

Use any list library functions(such as fold or to

Info iconThis preview shows pages 3–7. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: use any list library functions (such as fold , or @ ) to solve this problem. If you would like to use a helper function in your answer, you must define it. let rec intersperse (c:’a) (l:’a list) : ’a list = begin match l with | -> | [x] -> [x] | x::xs -> x::c::(intersperse c xs) end Grading scheme: • no deduction for minor syntax errors •-2 incorrect Nil case •-3 incorrect Singleton case •-5 Not recursing/pattern matching on correct list • various other errors at discretion 3 2. List Processing (20 points) For each of the following programs, write the value computed for r : a. let rec h (l:int list) : int = begin match l with | -> 0 | x::xs -> x * (h xs) end let r : int = h [1;2;3] b. let rec g (l:’a list) : ’a list = begin match l with | -> | [x] -> [x] | x::y::xs -> if x < y then x::(g (y::xs)) else y::(g (x::xs)) end let r : int list = g [1;3;2;0] [1;2;0;3] c. let rec f (p: ’a -> bool) (l:’a list) : ’a list * ’a list = begin match l with | -> (, ) | x::xs -> let (l,r) = f p xs in if p x then (x::l, r) else (l, x::r) end let r : (int list * int list) = f ( fun (x:int) -> x > 0) [0;1;2;-3;4] ([1;2;4], [0;-3]) 4 The last two programs refer to the following definitions. let rec transform (f: ’a -> ’b) (x: ’a list): ’b list = begin match x with | -> | h :: t -> (f h) :: (transform f t) end let rec fold (combine: ’a -> ’b -> ’b) (base: ’b) (x: ’a list): ’b = begin match x with | -> base | h :: t -> combine h (fold combine base t) end d. let k (x: ’a list) : ’a list = fold ( fun (h:’a) (v:’a list) -> v @ [h]) x let r : int list = k [1;3;2;4] [4;2;3;1] e. let j (x : int list list) : int list = let transformer (l:int list) : int = fold ( fun (x:int) (v:int) -> x + v) 0 l in transform transformer x let r : int list = j [[1;2;3];[4;5];] [6;9;0] Grading scheme, each answer worth four points: • no deduction for minor syntax errors • 1 point if the value is of the correct type • 2 points (part c) if structure is correct • 4 points if completely correct • Other minors errors -1 to -4 at discretion (e.g. -1 point per wrong list item/wrong order) 5 3. Types (16 points) For each OCaml value or function definition below, fill in the blank where the type annotation could go or write “ill typed” if there is a type error. If an expression can have multiple types, give the most generic one. We have done the first one for you....
View Full Document

{[ snackBarMessage ]}

Page3 / 10

use any list library functions(such as fold or to solve...

This preview shows document pages 3 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online