基于链表的Smalltalk素数生成器报错排查求助

核心问题分析 #

1. 自定义链表缺失迭代方法：PrimesGenerator的next方法调用了primes do: [...]，但自定义的ConnectedList未实现do:方法，这是运行时错误的直接原因。
2. 素数生成逻辑失效：next方法中value固定为3未递增，递归调用^self next会导致无限循环；whileTrue:的块返回值不符合预期，无法触发正确的循环逻辑。
3. 初始化方法不规范：Node和ConnectedList使用自定义init方法而非Smalltalk标准的initialize，可能导致实例变量未正确初始化。
4. 输出逻辑偏差：初始化时已存入素数2，但next方法仅返回后续生成的素数，导致最终输出缺失第一个素数。

修复方案与完整代码 #

1. 规范初始化方法 #

将Node和ConnectedList的初始化方法改为Smalltalk标准的initialize：

Object subclass: #Node
    instanceVariableNames: 'value next'
    classVariableNames: ''
    poolDictionaries: ''
    category: 'MyApplication'

!Node methodsFor: 'initialization'!
initialize
    "Initialize a new node"
    super initialize.
    value := nil.
    next := nil.
    ^self
! !

!Node methodsFor: 'accessing'!
value
    ^value
! !

!Node methodsFor: 'accessing'!
next
    ^next
! !

!Node methodsFor: 'accessing'!
setValue: anObject
    value := anObject
! !

!Node methodsFor: 'accessing'!
setNext: aNode
    next := aNode
! !

Object subclass: #ConnectedList
    instanceVariableNames: 'head tail'
    classVariableNames: ''
    poolDictionaries: ''
    category: 'MyApplication'

!ConnectedList methodsFor: 'initialization'!
initialize
    "Initialize a new connected list"
    super initialize.
    head := nil.
    tail := nil.
    ^self
! !

!ConnectedList methodsFor: 'accessing'!
head
    ^head
! !

!ConnectedList methodsFor: 'accessing'!
tail
    ^tail
! !

!ConnectedList methodsFor: 'accessing'!
isEmpty
    ^head isNil
! !

!ConnectedList methodsFor: 'adding'!
add: anObject
    | newNode |
    newNode := Node new.
    newNode setValue: anObject.
    newNode setNext: nil.

    head isNil
        ifTrue: [
            head := newNode.
            tail := newNode.
        ]
        ifFalse: [
            tail setNext: newNode.
            tail := newNode.
        ]
    ^self
! !

!ConnectedList methodsFor: 'enumerating'!
do: aBlock
    "遍历链表并执行传入的块"
    | currentNode |
    currentNode := head.
    [ currentNode isNil ] whileFalse: [
        aBlock value: currentNode value.
        currentNode := currentNode next.
    ]
! !

2. 修正素数生成逻辑 #

重写PrimesGenerator的next方法，加入递增逻辑与素数判断优化：

Object subclass: #PrimesGenerator
    instanceVariableNames: 'primes'
    classVariableNames: ''
    poolDictionaries: ''
    category: 'MyApp-PrimesGenerator'

!PrimesGenerator class methodsFor: 'instance creation'!
new
    ^self basicNew initialize
! !

!PrimesGenerator methodsFor: 'initialization'!
initialize
    primes := ConnectedList new.
    primes add: 2.
    ^self
! !

!PrimesGenerator methodsFor: 'accessing'!
primes
    ^primes
! !

!PrimesGenerator methodsFor: 'generating primes'!
next
    "返回下一个素数"
    | value isPrime |
    value := primes tail value + 1.

    [
        isPrime := true.
        primes do: [ :each |
            "优化：只需检查到value的平方根"
            each * each > value ifTrue: [ ^value ].
            value \\ each = 0 ifTrue: [
                isPrime := false.
                value := value + 1.
                ^self next.
            ]
        ].
        isPrime
    ] whileFalse.

    primes add: value.
    ^value
! !

3. 调整输出逻辑 #

确保输出包含初始化的第一个素数：

generator := PrimesGenerator new.

"先输出初始素数2"
Transcript show: generator primes head value; cr.

"生成并输出后续4个素数"
1 to: 4 do: [ :i |
    Transcript show: generator next; cr.
].

预期输出 #

2
3
5
7
11

内容的提问来源于stack exchange，提问作者GearedInsanity