大约有 15,000 项符合查询结果（耗时：0.0588秒） [XML]
convert double to int
...maller than the range of double. A cast from double to int won't throw an exception if the value is outside the range of int in an unchecked context, whereas a call to Convert.ToInt32(double) will. The result of the cast (in an unchecked context) is explicitly undefined if the value is outside the r...
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...
UIRefreshControl - beginRefreshing not working when UITableViewController is inside UINavigationCont
...ViewController (which is inside a UINavigationController) and it works as expected (i.e. pull down fires the correct event). However, if I programmatically invoke the beginRefreshing instance method on the refresh control like:
...
How to map and remove nil values in Ruby
...
Ruby 2.7+
There is now!
Ruby 2.7 is introducing filter_map for this exact purpose. It's idiomatic and performant, and I'd expect it to become the norm very soon.
For example:
numbers = [1, 2, 5, 8, 10, 13]
enum.filter_map { |i| i * 2 if i.even? }
# => [4, 16, 20]
In your case, as the bl...
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 ...
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
...
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...
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?
...
Does Python support short-circuiting?
Does Python support short-circuiting in boolean expressions?
3 Answers
3
...