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Why is string concatenation faster than array join?
...tenation:
// ECMA-262, section 15.5.4.6
function StringConcat() {
if (IS_NULL_OR_UNDEFINED(this) && !IS_UNDETECTABLE(this)) {
throw MakeTypeError("called_on_null_or_undefined", ["String.prototype.concat"]);
}
var len = %_ArgumentsLength();
var this_as_string = TO_STRING_INLINE(t...
Applying a function to every row of a table using dplyr?
...f Hadley's examples using pmap:
iris %>%
mutate(Max.Len= purrr::pmap_dbl(list(Sepal.Length, Petal.Length), max))
Using this approach, you can give an arbitrary number of arguments to the function (.f) inside pmap.
pmap is a good conceptual approach because it reflects the fact that when ...
When should I use C++ private inheritance?
...ly, which is not the case with plain inheritance.
– j_random_hacker
Mar 18 '09 at 8:23
5
This can...
More elegant way of declaring multiple variables at the same time
...ension, but here's a very readable implementation:
>>> def invert_dict(inverted_dict):
... elements = inverted_dict.iteritems()
... for flag_value, flag_names in elements:
... for flag_name in flag_names:
... yield flag_name, flag_value
...
>>> flags =...
How to force use of overflow menu on devices with menu button
...droid.com/apk/res/android" >
<item
android:id="@+id/menu_overflow"
android:icon="@drawable/abs__ic_menu_moreoverflow_normal_holo_light"
android:orderInCategory="11111"
android:showAsAction="always">
<menu>
<item
...
Vagrant stuck connection timeout retrying
...anage list runningvms
This will result in something like this:
"projects_1234567890" {5cxxxx-cxxx-4xxx-8xxx-5xxxxxxxxxx}
Quite often, the VM is simply waiting for you to select an option in the bootloader. You can send the appropriate keycode (in the case, Enter) to the vm with controlvm:
vbo...
How do I parse a string to a float or int?
...
Python method to check if a string is a float:
def is_float(value):
try:
float(value)
return True
except:
return False
A longer and more accurate name for this function could be: is_convertible_to_float(value)
What is, and is not a float in Python may surpris...
how to clear the screen in python [duplicate]
... To avoid the 0 (system's return value) being shown, use absolutely_unused_variable = os.system("cls") or absolutely_unused_variable = os.system("clear")
– Shiva
Jul 4 '15 at 8:01
...
CMap用法 - C/C++ - 清泛网 - 专注C/C++及内核技术
...的效率。CMap就是对Hash表的一种实现。先上实例：
int _tmain(int argc, char* argv[])
{
//定义
typedef CMap<int, int, CString, CString> CMapInt;
CMapInt map;
//添加key，val
map.SetAt(1, "str1");
map.SetAt(2, "str2");
map.SetAt(3, "str3");
map.SetAt(1, "s...
error: cannot dynamic_cast ‘b’ (of type ‘class Base*’) to type ‘c...
error: cannot dynamic_cast ‘b’ (of type ‘class Base*’) to type ‘class Derived*’ (source type is not polymorphic)在将父类型转换为子类型时,可以使用static_cast和dynamic_cast.如果使用dynamic_cast,它要求父类必须为多态的,即要求至少有一个虚函数,因此....