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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...
How to pipe stdout while keeping it on screen ? (and not to a output file)
...on some non Unix environments like cygwin too.
echo 'ee' | tee /dev/tty | foo
Reference: The Open Group Base Specifications Issue 7
IEEE Std 1003.1, 2013 Edition, §10.1:
/dev/tty
Associated with the process group of that process, if any. It is
useful for programs or shell procedures ...
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...
Easiest way to convert a List to a Set in Java
...
Set<Foo> foo = new HashSet<Foo>(myList);
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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...
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
...