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How is a CRC32 checksum calculated?
... 1 0000 0100 1100 0001 0001 1101 1011 0111
The highest term (x32) is usually not explicitly written, so it can instead be represented in hex just as
0x 04 C1 1D B7
Feel free to count the 1s and 0s, but you'll find they match up with the polynomial, where 1 is bit 0 (or the first bit) and x ...
Finding the index of elements based on a condition using python list comprehension
...
In Python, you wouldn't use indexes for this at all, but just deal with the values—[value for value in a if value > 2]. Usually dealing with indexes means you're not doing something the best way.
If you do need an API similar to Matlab's, you would use numpy, a packag...
Why #define TRUE (1==1) in a C boolean macro instead of simply as 1?
...type (and resolve to true and false) if the compiler supports it. (specifically, C++)
However, it would be better to check whether C++ is in use (via the __cplusplus macro) and actually use true and false.
In a C compiler, this is equivalent to 0 and 1.
(note that removing the parentheses will bre...
Can't access object property, even though it shows up in a console log
...g)) and you will see the keys, or the state of the object at the time you called console.log.
You will (usually) find the keys are being added after your console.log call.
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UIRefreshControl without UITableViewController
...ng a UIRefreshControl instance as a subview to my UITableView. And it magically just works!
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:@selector(handleRefresh:) forControlEvents:UIControlEventValueChanged];
[self.myTableView addSubview:...
What is the difference between String.Empty and “” (empty string)?
...ich makes string.Empty more efficient.
In version 2.0 and later of .NET, all occurrences of "" refer to the same string literal, which means "" is equivalent to .Empty, but still not as fast as .Length == 0.
.Length == 0 is the fastest option, but .Empty makes for slightly cleaner code.
See the ...
Setting the correct encoding when piping stdout in Python
...you must encode it yourself.
A rule of thumb is: Always use Unicode internally. Decode what you receive, and encode what you send.
# -*- coding: utf-8 -*-
print u"åäö".encode('utf-8')
Another didactic example is a Python program to convert between ISO-8859-1 and UTF-8, making everything upper...
How to calculate a time difference in C++
...turns the CPU time consumed by the program. So if the program is run in parallel the time returned by the function would be the accumulated of the time spent on all CPUs, rather than the time elapsed cplusplus.com/reference/ctime/clock
– Ameer Jewdaki
Aug 3 '1...
Do htmlspecialchars and mysql_real_escape_string keep my PHP code safe from injection?
... is effectively just a string escaping function. It is not a magic bullet. All it will do is escape dangerous characters in order that they can be safe to use in a single query string. However, if you do not sanitise your inputs beforehand, then you will be vulnerable to certain attack vectors.
Ima...
How to convert a String to its equivalent LINQ Expression Tree?
...nking as a Where clause. If necessary, put it inside a list/array just to call .Where(string) on it! i.e.
var people = new List<Person> { person };
int match = people.Where(filter).Any();
If not, writing a parser (using Expression under the hood) isn't hugely taxing - I wrote one similar (a...