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Capturing Groups From a Grep RegEx
... to first reduce your line to a known format, and then to extract just the bit you want. (Although tools like cut and sed are far better at this).
Suppose for the sake of argument that your pattern was a bit simpler: [0-9]+_([a-z]+)_ You could extract this like so:
echo $name | grep -Ei '[0-9]+_[a...
std::vector performance regression when enabling C++11
... ( +- 2.05% )
Indeed, if we ask the compiler to try just a little bit harder to inline that function, the difference in performance goes away.
So what is the take away from this story? That failed inlines can cost you a lot and you should make full use of the compiler capabilities: I can...
Python's time.clock() vs. time.time() accuracy?
...he function to use for
benchmarking Python or timing algorithms.
On Windows, this function returns wall-clock seconds elapsed since the
first call to this function, as a floating point number, based on the
Win32 function QueryPerformanceCounter(). The resolution is typically
better than...
0.1 float is greater than 0.1 double. I expected it to be false [duplicate]
...the rounding mode when converting the double to float. float has 24 binary bits of precision, and double has 53. In binary, 0.1 is:
0.1₁₀ = 0.0001100110011001100110011001100110011001100110011…₂
^ ^ ^ ^
1 10 20 24
So if we round up ...
Fundamental difference between Hashing and Encryption algorithms
...I'll do my best here:
Hash Functions
They provide a mapping between an arbitrary length input, and a (usually) fixed length (or smaller length) output. It can be anything from a simple crc32, to a full blown cryptographic hash function such as MD5 or SHA1/2/256/512. The point is that there's a o...
“f” after number
...jective-C; putting an f on the end - 0.0f - declares the constant as a (32-bit) float.)
CGRect frame = CGRectMake(0, 0, 320, 50);
uses ints which will be automatically converted to floats.
In this case, there's no (practical) difference between the two.
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How to check the version before installing a package using apt-get?
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How to set custom favicon in Express?
...0/favicon.ico returns Cannot GET /favicon.ico.
– user1063287
Sep 20 at 3:23
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What does |= (ior) do in Python?
... an update operation
counters: a union (of multisets) operation
numbers: a bitwise OR, binary operation
In most cases, it is related to the | operator. See examples below.
Sets
For example, the union of two assigned sets s1 and s2 share the following equivalent expressions:
>>> s1 = s1 | ...
Why are unnamed namespaces used and what are their benefits?
... then you said 3 vs 4 seconds are "the same time". neither of these make a bit of sense. i suspect the real explanation would, but what is it?
– underscore_d
Dec 25 '15 at 2:13
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