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Simulate CREATE DATABASE IF NOT EXISTS for PostgreSQL?
...
Restrictions
You can ask the system catalog pg_database - accessible from any database in the same database cluster. The tricky part is that CREATE DATABASE can only be executed as a single statement. The manual:
CREATE DATABASE cannot be executed inside a transaction b...
Validating with an XML schema in Python
...et's create simplest validator.py
from lxml import etree
def validate(xml_path: str, xsd_path: str) -> bool:
xmlschema_doc = etree.parse(xsd_path)
xmlschema = etree.XMLSchema(xmlschema_doc)
xml_doc = etree.parse(xml_path)
result = xmlschema.validate(xml_doc)
return result...
What is the (function() { } )() construct in JavaScript?
...nswered Nov 22 '11 at 14:21
gion_13gion_13
38.3k99 gold badges9090 silver badges101101 bronze badges
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C# 4 default parameter values: How to assign a default DateTime/object value? [duplicate]
...opt] int32 x) cil managed
{
.param [1] = int32(5)
.maxstack 8
L_0000: nop
L_0001: ret
}
.method //this is a new method
private hidebysig static //it is private, ???, and static
void foo //it returns nothing (void) and is named Foo
([opt] int32 x) //it has one parameter, which i...
How to use a variable to specify column name in ggplot
...string that the variable contains, using sym()(which is almost the same as base aliases as.name() / as.symbol()), and unquote it using !!
Simulating OP's data we can do :
library(tidyverse)
rates.by.groups <- data.frame(
name = LETTERS[1:3],
rate = 1:3,
mjr = LETTERS[c(4,4,5)],
gender =...
Read a text file using Node.js?
... for help, clarification, or responding to other answers.Making statements based on opinion; back them up with references or personal experience.To learn more, see our tips on writing great answers.
Draft saved
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Create a pointer to two-dimensional array
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Here you wanna make a pointer to the first element of the array
uint8_t (*matrix_ptr)[20] = l_matrix;
With typedef, this looks cleaner
typedef uint8_t array_of_20_uint8_t[20];
array_of_20_uint8_t *matrix_ptr = l_matrix;
Then you can enjoy life again :)
matrix_ptr[0][1] = ...;
Beware of...
How to convert nanoseconds to seconds using the TimeUnit enum?
...:
long elapsedTime = end - start;
double seconds = (double)elapsedTime / 1_000_000_000.0;
If you use TimeUnit to convert, you'll get your result as a long, so you'll lose decimal precision but maintain whole number precision.
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Is std::vector so much slower than plain arrays?
...;g = 0;
j->b = 0;
}
Result:
# ./vector
UseArray completed in 3.264 seconds
UseVector completed in 5.443 seconds
Nope, no different. At least it's not slower. I thought this would have performance similar to #2 where I used a Pixel& reference.
Conclusion
Even if some smart cookie f...
PHP mkdir: Permission denied problem
... AM ON MAC OSX LION
What happens is that apache is being run as the user "_www" and doesn't have permissions to edit any files. You'll notice NO filesystem functions work via php.
How to fix:
Open a finder window and from the menu bar, choose Go > Go To Folder > /private/etc/apache2
now op...