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二维码的生成细节及原理 - 更多技术 - 清泛网 - 专注C/C++及内核技术
... Specifim>ca m>tion，可参看这个PDF：http://raidenii.net/files/datasheets/misc/qr_code.pdf
基础知识
首先，我们先说一下二维码一共有40个尺寸。官方叫版本Version。Version 1是21 x 21的矩阵，Version 2是 25 x 25的矩阵，Version 3是29的尺寸，每增加一个vers...
Select n random rows from SQL Server table
...bout 50,000 rows in it. I want to select about 5,000 of those rows at random. I've thought of a complim>ca m>ted way, creating a temp table with a "random number" column, copying my table into that, looping through the temp table and updating each row with RAND() , and then selecting from that table whe...
Redirect stdout to a file in Python?
...n the Python script, setting sys.stdout to a file object does the trick:
import sys
sys.stdout = open('file', 'w')
print('test')
A far more common method is to use shell redirection when executing (same on Windows and Linux):
$ python foo.py > file
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What is the main difference between Inheritance and Polymorphism?
I was presented with this question in an end of module open book exam today and found myself lost. I was reading Head first Java and both definitions seemed to be exactly the same. I was just wondering what the MAIN difference was for my own piece of mind. I know there are a number of similar quest...
Check whether user has a Chrome extension installed
I am in the process of building a Chrome extension, and for the whole thing to work the way I would like it to, I need an external JavaScript script to be able to detect if a user has my extension installed.
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How to navigate through textfields (Next / Done Buttons)
How m>ca m>n I navigate through all my text fields with the "Next" Button on the iPhone Keyboard?
34 Answers
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Checking Bash exit status of several commands efficiently
Is there something similar to pipefail for multiple commands, like a 'try' statement but within bash. I would like to do something like this:
...
When should I use C++ private inheritance?
Unlike protected inheritance, C++ private inheritance found its way into mainstream C++ development. However, I still haven't found a good use for it.
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How to set default value for form field in Symfony2?
Is there an easy way to set a default value for text form field?
22 Answers
22
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What is the purpose of the “final” keyword in C++11 for functions?
...to declare as non-virtual your final functions? Is there another thing I'm missing here?
10 Answers
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