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Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
...just changing the elements that need to be changed. That's important to avoid for large data, and why := and set() were introduced to data.table.
Now, with our copied newDT we can modify it by reference :
newDT
# a b
# [1,] 1 11
# [2,] 2 200
newDT[2, b := 400]
# a b # See FA...
Git pull results in extraneous “Merge branch” messages in commit log
... to use rebasing instead of merging is possible, but usually you should avoid it. Rebasing allows you to keep a linear history, but also removes any information about the branching that originally happened. It will also cause the history of the current branch being rewritten, recreating all commits ...
What does “abstract over” mean?
...this really means we're integrating by the similarities.
For example, consider a program that takes the sum of the numbers 1, 2, and 3:
val sumOfOneTwoThree = 1 + 2 + 3
This program is not very interesting, since it's not very abstract. We can abstract over the numbers we're summing, by integrat...
What is the fastest integer division supporting division by zero no matter what the result is?
...
Inspired by some of the comments I got rid of the branch on my Pentium and gcc compiler using
int f (int x, int y)
{
y += y == 0;
return x/y;
}
The compiler basically recognizes that it can use a condition flag of the test in the addition.
As pe...
How do you validate a URL with a regular expression in Python?
...
An easy way to parse (and validate) URL's is the urlparse (py2, py3) module.
A regex is too much work.
There's no "validate" method because almost anything is a valid URL. There are some punctuation rules for splitting it up. Absent any punctuati...
Inheriting class methods from modules / mixins in Ruby
...
A common idiom is to use included hook and inject class methods from there.
module Foo
def self.included base
base.send :include, InstanceMethods
base.extend ClassMethods
end
module InstanceMethods
def bar1
'...
Call Go functions from C
...nt {
return a + b
}
// This is the public function, callable from outside this package.
// It forwards the parameters to C.doAdd(), which in turn forwards
// them back to goCallbackHandler(). This one performs the addition
// and yields the result.
func MyAdd(a, b int) int {
return int( C.do...
What's the need of array with zero elements?
...eof(*var) + extra, GFP_KERNEL);
This used to be not standard and was considered a hack (as Aniket said), but it was standardized in C99. The standard format for it now is:
struct bts_action {
u16 type;
u16 size;
u8 data[];
} __attribute__ ((packed)); /* Note: the __attribute__ is i...
Can I list-initialize a vector of move-only type?
...
Consider the in<T> idiom described on cpptruths (cpptruths.blogspot.com/2013/09/…). The idea is to determine lvalue/rvalue at run-time and then call move or copy-construction. in<T> will detect rvalue/lvalue even th...
Does PostgreSQL support “accent insensitive” collations?
...hen creating unaccent extension on PostgreSQL
Among other things, it provides the function unaccent() you can use with your example (where LIKE seems not needed).
SELECT *
FROM users
WHERE unaccent(name) = unaccent('João');
Index
To use an index for that kind of query, create an index on t...