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What happens if I define a 0-size array in C/C++?
...
An array cannot have zero size.
ISO 9899:2011 6.7.6.2:
If the expression is a constant expression, it shall have a value greater than zero.
The above text is true both for a plain array (paragraph 1). For a VLA (variable length array), the behavior is undefined if the expression's valu...
What happens to a declared, uninitialized variable in C? Does it have a value?
...ic variables (file scope and function static) are initialized to zero:
int x; // zero
int y = 0; // also zero
void foo() {
static int x; // also zero
}
Non-static variables (local variables) are indeterminate. Reading them prior to assigning a value results in undefined behavior.
void foo() {
...
postgresql - sql - count of `true` values
...select count(*) filter (where myCol)
from tbl;
The above query is a bad example in that a simple WHERE clause would suffice, and is for demonstrating the syntax only. Where the FILTER clause shines is that it is easy to combine with other aggregates:
select count(*), -- all
count(myCol), ...
How can I pass arguments to a batch file?
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Another useful tip is to use %* to mean "all". For example:
echo off
set arg1=%1
set arg2=%2
shift
shift
fake-command /u %arg1% /p %arg2% %*
When you run:
test-command admin password foo bar
the above batch file will run:
fake-command /u admin /p password admin password...
No line-break after a hyphen
...
You could also wrap the relevant text with
<span style="white-space: nowrap;"></span>
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Why is unsigned integer overflow defined behavior but signed integer overflow isn't?
...ed integer overflow is well defined by both the C and C++ standards. For example, the C99 standard ( §6.2.5/9 ) states
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How to merge lists into a list of tuples?
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@Adrien: cheers for your applicable comment. For Python 2.x, s/zip_longest()/izip_longest(). Renamed in Python 3.x to zip_longest().
– mechanical_meat
Jul 10 '11 at 19:13
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What is the correct way to document a **kwargs parameter?
I'm using sphinx and the autodoc plugin to generate API documentation for my Python modules. Whilst I can see how to nicely document specific parameters, I cannot find an example of how to document a **kwargs parameter.
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postgresql port confusion 5433 or 5432?
I have installed postgresql on OSX. When I run psql, I get
7 Answers
7
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Python: fastest way to create a list of n lists
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The probably only way which is marginally faster than
d = [[] for x in xrange(n)]
is
from itertools import repeat
d = [[] for i in repeat(None, n)]
It does not have to create a new int object in every iteration and is about 15 % faster on my machine.
Edit: Using NumPy, you can avoid t...