《Two Dozen Short Lessons in Haskell》(二十四)代数类型

这是《Two Dozen Short Lessons in Haskell》这本书的最后一章,第23章没有习题。




1 A tree, in computer science, is an entity

a with a root and two subtrees

b with a root and a collection of subtrees, each of which is also a tree

c with a collection of subtrees, each of which has one or more roots

d described in a diagram with circles, lines, and random connections


2 A sequence, in Haskell, is an entity

a with one or more elements

b that is empty or has a first element followed by a sequence of elements

c whose elements are also sequences

d with a head and one or more tails


3 The following definition specifies


HASKELL DEFINITION • Monday | Tuesday | Wednesday | Thursday | Friday

a a type with five constructors

b a type with five explicit constructors and two implicit ones

c a tree with five roots

d a sequence with five elements


4 Given the definition in the preceding question, what is the type of the following function f?

HASKELL DEFINITION • f Tuesday = "Belgium"

a f :: WeekDay –> String

b f :: Tuesday -> "Belgium"

c f :: Day –> Country

d type of f cannot be determined


5 Types defined in Haskell scripts with the data keyword

a must begin with a capital letter

b may be imported from modules

c must be used consistently in formulas, just like intrinsic types

d all of the above


6 What kind of structure does the following type represent?

HASKELL DEFINITION • data BinaryTree = Branch BinaryTree BinaryTree | Leaf String

a a type with four constructors

b a digital structure

c a tree made up of ones and zeros

d a tree in which each root has either two subtrees or none


7 Given the preceding definition of the type BinaryTree, which of the following defines a function that computes

the total number of Branch constructors in an entity of type BinaryTree?

a branches binaryTree = 2

b branches (Branch left right) = 2

branches (Leaf x) = 0

c branches (Branch left right) = 1 + branches left + branches right

branches (Leaf x) = 0

d branches (Branch left right) = 2*branches left + 2*branches right

branches (Leaf x) = 1


8 The formula xs!!(length xs - 1)

a is recursive

b has the same type as xs

c delivers the same result as last xs

d none of the above


9 Given the definition of the function pam in the module SequenceUtilities, the formula

pam (map (+) [1 . . 5]) 10

a delivers the same result as map (1+) [1 . . 5]

b delivers the same result as pam [1 .. 5] (map (1+))

c delivers the result [11, 12, 13, 14, 15]

d all of the above


10 Given the Grid [1,3,0, 0,0,0, 0,0,2] (as in the tic-tac-toe script), what is the status of the game?

a game over, X wins

b game over, O wins

c O’s turn to play

d X’s turn to play


11 Which of the following formulas extracts the diagonal of a grid (as in the tic-tac-toe program)?

a (take 3 . map head . iterate(drop 4)) grid

b [head grid, head(drop 4 grid), head(drop 8 grid)]

c [head grid, grid!!4, last(grid)]

d all of the above







1 b



2 b



3 a



4 a



5 d



6 d



7 c



8 c



9 c?



10 c


130   XX.

000   …

002   ..O


11 b?


posted @ 2013-09-05 09:33  申龙斌的程序人生  阅读(813)  评论(0编辑  收藏  举报