大约有 12,000 项符合查询结果（耗时：0.0293秒） [XML]
variable === undefined vs. typeof variable === “undefined”
...
For undeclared variables, typeof foo will return the string literal "undefined", whereas the identity check foo === undefined would trigger the error "foo is not defined".
For local variables (which you know are declared somewhere), no such error would occu...
Understanding PrimeFaces process/update and JSF f:ajax execute/render attributes
...certain command component is invoked ain't gonna work:
<p:inputText id="foo" value="#{bean.foo}" />
<p:commandButton process="foo" action="#{bean.action}" />
It would only process the #{bean.foo} and not the #{bean.action}. You'd need to include the command component itself as well:
<...
How to return a string value from a Bash function
... return.
#!/bin/bash
set -x
function pass_back_a_string() {
eval "$1='foo bar rab oof'"
}
return_var=''
pass_back_a_string return_var
echo $return_var
Prints "foo bar rab oof".
Edit: added quoting in the appropriate place to allow whitespace in string to address @Luca Borrione's comment.
E...
How to access pandas groupby dataframe by key
...
You can use the get_group method:
In [21]: gb.get_group('foo')
Out[21]:
A B C
0 foo 1.624345 5
2 foo -0.528172 11
4 foo 0.865408 14
Note: This doesn't require creating an intermediary dictionary / copy of every subdataframe for every group, so will be muc...
How to define an empty object in PHP
...e objects of anonymous type in JavaScript:
//JavaScript
var myObj = {
foo: "Foo value",
bar: "Bar value"
};
console.log(myObj.foo); //Output: Foo value
So I always try to write this kind of objects in PHP like javascript does:
//PHP >= 5.4
$myObj = (object) [
"foo" => "Foo valu...
Easiest way to convert a List to a Set in Java
...
Set<Foo> foo = new HashSet<Foo>(myList);
share
|
improve this answer
|
follow
...
C++常用排序算法汇总 - C/C++ - 清泛网 - 专注C/C++及内核技术
...{n^2}
* 从末尾开始，与上个元素比较并交换
* 每轮都将能最小的元素换到首位
*
* https://www.tsingfun.com
************************************/
#include<stdio.h>
#include<stdlib.h>
/*
冒泡排序后的顺序为从小到大
*/
void Bubble_Sort(int *arr,int le...
redirect COPY of stdout to log file from within bash script itself
...al from him by simply
# adding his answer to mine.
exec 2>&1
echo "foo"
echo "bar" >&2
Note that this is bash, not sh. If you invoke the script with sh myscript.sh, you will get an error along the lines of syntax error near unexpected token '>'.
If you are working with signal tr...
Explicitly calling return in a function or not
...ction and easily see all exit points and values.
Paul used this example:
foo = function() {
if(a) {
return(a)
} else {
return(b)
}
}
Unfortunately, one could point out that it can easily be rewritten as:
foo = function() {
if(a) {
output <- a
} else {
output <- b
}
outpu...
RAII and smart pointers in C++
...e stack. For instance (and stealing an example from another answer):
void foo() {
std::string str;
// Do cool things to or using str
}
This works fine - but what if we want to return str? We could write this:
std::string foo() {
std::string str;
// Do cool things to or using str
...