Transactional Stack & Recursion

January 26, 2021

Bilgisayarımdan çıkan bir başka soru ile sizinleyim. Sorumuz şu şekilde, öyle bir stack implement etmek istiyorsunuz ki bu aynı zamanda transactional davranışlar göstersin. Diğer değişle (begin, commit, rollback) fonksiyonları içeren bir stack yazalım.

Hemen örneğe geçelim.

1
2
3
4
5
6
7

> yeni transaction aç
> 5 ekle
> yeni transaction aç
> 3 ekle
> 6 ekle
> transaction ı rollback et
> transactıon ı commit et

Bunu elle işletelim.

1
2
3
4
5
6
7

> yeni transaction aç -> []
> 5 ekle -> [5]
> yeni transaction aç -> [5, []]
> 3 ekle -> [5, [3]]
> 6 ekle -> [5, [3, 6]]
> transaction ı rollback et -> [5]
> transactıon ı commit et -> [5]

Python 2.7 ne kadar tipler belli olmasa da aşağıdakine benzer bir veri yapısı kullandım.

1
2
3
4
5
6
7
8
9

class TransactionalStack:
    content = [] # stack<Any>
    nested_tx = [] # stack<TransactionalStack>
    def push(self, value: Any): pass
    def pop(self): pass
    def top(self): pass
    def begin(self): pass
    def commit(self): pass
    def rollback(self): pass

Böylelikle istediğiniz kadar iç içe transaction kullanabilirsiniz. Kodun tamamını paylaşayım.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

class TransactionalStack(object):
    def __init__(self, content = []):
        self.content = [content]
        self.nested_tx = [self]

    def begin(self):
        tx = TransactionalStack(self.content)
        self.nested_tx.append(tx)

    def push(self, value):
        self.nested_tx[-1].content.append(value)

    def pop(self):
        last_tx_values = self.nested_tx[-1].content
        return (last_tx_values.pop() if last_tx_values else 0)

    def top(self):
        last_tx_values = self.nested_tx[-1].content
        return (last_tx_values.pop() if last_tx_values else 0)

    def commit(self):
        last_tx = self.nested_tx[-1]
        if last_tx != self:
            last_tx = self.nested_tx.pop()
            self.nested_tx[-1].content = last_tx.content
            return True
        return False

    def rollback(self):
        last_tx = self.nested_tx[-1]
        if last_tx != self:
            self.nested_tx.pop()
            return True
        return False

ts = TransactionalStack()
ts.push(4)
ts.begin() # tx1 basladi
ts.push(7) # tx1 degerleri [4, [7]]
ts.begin() # tx2 basladi
ts.push(2) # tx2 degeleri [4, [7, [2]]]
print ts.rollback() # tx2 rolledback edildi [4, [7]]
print ts.top() # tx1' en ustteki degeri 7
ts.begin() # tx3 basladi
ts.push(10) # degerleri [4, [7, [10]]]
print ts.commit() # tx3 commit edildi
print ts.top() # tx3 un en ustteki degeri
print ts.rollback() # tx2 rollback edildi
print ts.top() # tx1 en ustteki degeri
print ts.commit() # false # acik transaction kalmadi.
« Conditional Formatting
Darwin Project ve Bölgeler »

hidden

John von Neumann – The Man from the Future

Before I read The Man from the Future by Ananyo Bhattacharya, I only knew about John von Neumann in two contexts: that computers use the von Neumann architecture, and that he appeared in a story about a mathematical problem I … Continue reading →

via Henrik Warne's blog

The Review Is the Action Item

2024/05/30The Review Is the Action ItemI like to consider running an incident review to be its own action item. Other follow-ups emerging from it are a plus, but the point is to learn from incidents, and the review gives room for that to happen.This is no…

via Ferd.ca

HOWTO: Change your behavior

In theory, behavior change should be easy. At first glance, it seems like you control your behavior. So, if you desire different behavior, why doesn’t your behavior change as instantly as your desire to change it? In short, lasting change of habitual behavio…

via Matt Might's blog