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How to overload std::swap()
...ment-dependent lookup (ADL). One particularly easy thing to do is:
class X
{
// ...
friend void swap(X& a, X& b)
{
using std::swap; // bring in swap for built-in types
swap(a.base1, b.base1);
swap(a.base2, b.base2);
// ...
swap(a.member1...
Python: Append item to list N times
... and you may wish to modify later (like sub-lists, or dicts):
l = [{} for x in range(100)]
(The reason why the first method is only a good idea for constant values, like ints or strings, is because only a shallow copy is does when using the <list>*<number> syntax, and thus if you did ...
Creating an empty Pandas DataFrame, then filling it?
...
Here's a couple of suggestions:
Use date_range for the index:
import datetime
import pandas as pd
import numpy as np
todays_date = datetime.datetime.now().date()
index = pd.date_range(todays_date-datetime.timedelta(10), periods=10, freq='D')
columns = ['A','B', 'C']
Note: we cou...
Test if lists share any items in python
... Python, searching them is O(1) (see here for more information about complexity of operators in Python). Theoretically, this is O(n+m) on average for n and m objects in lists a and b. But 1) it must first create sets out of the lists, which can take a non-negligible amount of time, and 2) it suppose...
Does Python support short-circuiting?
Does Python support short-circuiting in boolean expressions?
3 Answers
3
...
Which is faster: while(1) or while(2)?
...with an optimization flag):
With -O0:
.file "main.c"
.intel_syntax noprefix
.def __main; .scl 2; .type 32; .endef
.text
.globl main
.def main; .scl 2; .type 32; .endef
.seh_proc main
main:
push rbp
.seh_pushreg rbp
mov rbp, rsp
...
Where does Scala look for implicits?
...ever seems to get fully formed, as if there weren't words for it. :-) For example, where do the values for integral below come from?
...
Match multiple cases classes in scala
...C(_) => "B"
case _ => "default"
}
}
If you must, must, must extract the parameter and treat them in the same code block, you could:
def matcher(l: Foo): String = {
l match {
case A() => "A"
case bOrC @ (B(_) | C(_)) => {
val s = bOrC.asInstanceOf[{def s: String}]...
Creating my own Iterators
...ber of templates and concepts to implement new iterators and adapters for existing iterators. I have written an article about this very topic; it's in the December 2008 ACCU magazine. It discusses an (IMO) elegant solution for exactly your problem: exposing member collections from an object, using B...
Aggregate / summarize multiple variables per group (e.g. sum, mean)
From a data frame, is there a easy way to aggregate ( sum , mean , max et c) multiple variables simultaneously?
8 Answer...