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Why always ./configure; make; make install; as 3 separate steps?
...ter to install certain libraries and files to certain directories. It is said to run ./configure, but in fact you should change it always.
For example have a look at the Arch Linux packages site. Here you'll see that any package uses a different configure parameter (assume they are using autotools...
What is the difference between “#!/usr/bin/env bash” and “#!/usr/bin/bash”?
...fferent systems. As long as it's in your path, it will find it.
One downside is that you will be unable to pass more than one argument (e.g. you will be unable to write /usr/bin/env awk -f) if you wish to support Linux, as POSIX is vague on how the line is to be interpreted, and Linux interprets e...
Difference between Big-O and Little-O Notation
...d ≤ 1
not ≤ 0, < 0, or < 1
Here's a table, showing the general idea:
(Note: the table is a good guide but its limit definition should be in terms of the superior limit instead of the normal limit. For example, 3 + (n mod 2) oscillates between 3 and 4 forever. It's in O(1) despite not...
Is calculating an MD5 hash less CPU intensive than SHA family functions?
...comparable efforts at optimizations; thus the speed differences can be considered as really intrinsic to the functions.
As a point of comparison, consider that a recent hard disk will run at about 100 MB/s, and anything over USB will top below 60 MB/s. Even though SHA-256 appears "slow" here, it is...
Can someone explain __all__ in Python?
...list of public objects of that module, as interpreted by import *. It overrides the default of hiding everything that begins with an underscore.
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Understanding NSRunLoop
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A run loop is an abstraction that (among other things) provides a mechanism to handle system input sources (sockets, ports, files, keyboard, mouse, timers, etc).
Each NSThread has its own run loop, which can be accessed via the currentRunLoop method.
In general, you do not need to ...
public friend swap member function
In the beautiful answer to the copy-and-swap-idiom there is a piece of code I need a bit of help:
2 Answers
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What do
...n only be used if this is a Foo[String]
def getStringLength(implicit evidence: A =:= String) = a.length
}
The implicit argument evidence is supplied by the compiler, iff A is String. You can think of it as a proof that A is String--the argument itself isn't important, only knowing that it exis...
List of Delphi language features and version in which they were introduced/deprecated
...elphi 1 Features
The full list from Embarcadero: What's New
See also: David I's list
To summarize:
Delphi 10.3.x, 10.4 (not yet out, this is speculative)
Custom managed records
Nullable types
Support for macOS 64-bit
Support for Android 64-bit
Delphi 10.3
The 64-bit Linux compil...
Filter rows which contain a certain string
...:
dplyr::filter(df, !grepl("RTB",TrackingPixel))
Since you have not provided the original data, I will add a toy example using the mtcars data set. Imagine you are only interested in cars produced by Mazda or Toyota.
mtcars$type <- rownames(mtcars)
dplyr::filter(mtcars, grepl('Toyota|Mazda', ...