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

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 • data WeekDay =

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

d all of the above

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1 b

2 b

3 a

data可以来自定义一种类型（也就是面向对象语言中的类），这里有五个构造器constructor。只是这里的构造器都没有带参数。

4 a

5 d

6 d

7 c

8 c

!!用来取出一个列表中指定位置上的元素。这里就是取最后一个元素，与last函数一样。

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(837)  评论(0编辑  收藏  举报