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Key to CSE341 Sample Midterm handout #6
1. Expression Value
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reduce(uncurry( * ), 3--5) 60
map(List.hd % List.tl, [9; 5; 8; 9]
[8--12; 4--9; 7--8; 8--10])
map((fun x -> x mod 4), 1--7) [1; 2; 3; 0; 1; 2; 3]
reduce(uncurry(+), 30
map((fun x -> x * x), 1--4))
filter((fun x -> x mod 4 > 1), 1--12) [2; 3; 6; 7; 10; 11]
map((fun x -> "(" ^ x ^ ")"), words) ["(live)"; "(long)";
"(and)"; "(prosper)"]
reduce(uncurry(@), [1--3; 4--6; 5--7]) [1; 2; 3; 4; 5; 6; 5;
6; 7]
map((fun x -> float_of_int(x) +. 0.5), 1--4) [1.5; 2.5; 3.5; 4.5]
reduce(uncurry(+), map(String.length, words)) 18
reduce(uncurry( * ), 105
map((fun x -> 2 * x - 1), 2--4))
2. Expression Type
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lst (string * int) list
[List.tl(lst)] (string * int) list list
(8, [["a"; "b"]; ["c"; "d"]]) int * string list list
fun x -> (List.hd(x) mod 3, List.tl(x)) int list -> int * int list
float_of_int % List.hd % List.tl int list -> float
3. The binding is:
val answer = 199
4. One possible solution appears below.
let sum_positives = reduce2 (+) % filter2 ((<) 0)
let strip = map2 (implode % reverse % List.tl % reverse % explode)
5. One possible solution appears below.
let powers(n, m) =
let rec loop(i, product) =
if i = 0 then [product]
else product::loop(i - 1, product * m)
in loop(n, 1)
6. One possible solution appears below.
let sorted_chars(s) = implode(qsort(uncurry(<),
map(Char.lowercase_ascii, filter(is_alpha, explode(s)))))
7. One possible solution appears below.
let rec interleave(params) =
match params with
| ([], ys) -> ys
| (xs, []) -> xs
| x::xs, y::ys -> x::y::interleave(xs, ys)
8. One possible solution appears below.
let rec nodes(tree) =
match tree with
| Empty -> 0
| Node(_, left, right) -> 1 + nodes(left) + nodes(right)
let rec leaves(tree) =
match tree with
| Empty -> []
| Node(root, Empty, Empty) -> [root]
| Node(_, left, right) -> leaves(left) @ leaves(right)
9. One possible solution appears below.
let rec cartesian_product(list1, list2) =
match list1 with
| [] -> []
| x::xs ->
map((fun y -> (x, y)), list2) @ cartesian_product(xs, list2)
let product(xs, ys) = map((fun (x, y) -> x * y),
cartesian_product(xs, ys))
10. One possible solution appears below.
let rec factors(list) =
match list with
| [(p, n)] -> powers(n, p)
| (p, n)::rest -> product(powers(n, p), factors(rest))
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