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What's “P=NP?”, and why is it such a famous question? [closed]
The question of whether P=NP is perhaps the most famous in all of Computer Science. What does it mean? And why is it so interesting?
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What is referential transparency?
...ther words, it is the closest subject outside computer science to what we call programming language semantics. The philosopher Willard Quine was responsible for initiating the concept of referential transparency, but it was also implicit in the approaches of Bertrand Russell and Alfred Whitehead.
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What are the functional differences between NW.js, Brackets-Shell and Electron?
...ide on node-webkit is node.js and npm. The package management of npm is really nice, and node has well done filesystem access.
Brackets-shell looked interesting, but other than a nice IDE I didn't really get what made this one as good or better than the rest. They are very clear that "The bracket...
How to force an entire layout View refresh?
...Invalidate the whole view. If the view is visible, onDraw(Canvas) will be called at some point in the future. This must be called from a UI thread. To call from a non-UI thread, call postInvalidate().
ViewGroup vg = findViewById (R.id.mainLayout);
vg.invalidate();
Now, when the Activity resume...
Why does one often see “null != variable” instead of “variable != null” in C#?
...r (and is indeed legal code):
// Probably wrong
if (x = 5)
when you actually probably meant
if (x == 5)
You can work around this in C by doing:
if (5 == x)
A typo here will result in invalid code.
Now, in C# this is all piffle. Unless you're comparing two Boolean values (which is rare, IME...
Counting the number of elements with the values of x in a vector
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Don't forget about potential floating point issues, especially with table, which coerces numbers to strings.
– hadley
Dec 17 '09 at 18:10
4
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log4j logging hierarchy order
...assigns a priority/severity level to the logging message. If the logging really takes effect (the message will be visible) depends on the effective logging level of the logger being used.
– Wolf
Oct 6 '17 at 6:18
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Combined area of overlapping circles
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Find all circle intersections on the outer perimeter (e.g. B,D,F,H on the following diagram). Connect them together with the centres of the corresponding circles to form a polygon. The area of the union of the circles is the area ...
Linux: compute a single hash for a given folder & contents?
...to/folder -type f -print0 | sort -z | xargs -0 sha1sum | sha1sum
And, finally, if you also need to take account of permissions and empty directories:
(find path/to/folder -type f -print0 | sort -z | xargs -0 sha1sum;
find path/to/folder \( -type f -o -type d \) -print0 | sort -z | \
xargs -0...
Why is #!/usr/bin/env bash superior to #!/bin/bash?
...or example, on my OpenBSD system, it's in /usr/local/bin, since it was installed as an optional package.
If you are absolutely sure bash is in /bin and will always be, there's no harm in putting it directly in your shebang—but I'd recommend against it because scripts and programs all have lives b...