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What is std::move(), and when should it be used?
...er that you would like to continue considering the reference as an rvalue.
foo(3 * 5); // obviously, you are calling foo with a temporary (rvalue)
int a = 3 * 5;
foo(a); // how to tell the compiler to treat `a` as an rvalue?
foo(std::move(a)); // will call `foo(int&& a)` rather than `fo...
How do I run two commands in one line in Windows CMD?
...is on all Microsoft OSes since 2000, and still good today:
dir & echo foo
If you want the second command to execute only if the first exited successfully:
dir && echo foo
The single ampersand (&) syntax to execute multiple commands on one line goes back to Windows XP, Windows 2...
How to access a dictionary element in a Django template?
...s the following lookups, in
this order:
Dictionary lookup (e.g., foo["bar"])
Attribute lookup (e.g., foo.bar)
Method call (e.g., foo.bar())
List-index lookup (e.g., foo[2])
The system uses the first lookup type
that works. It’s short-circuit logic.
...
What exactly does Perl's “bless” do?
...s stored in $obj (associated by bless with package "Class"), then $obj->foo(@args) will call a subroutine foo and pass as first argument the reference $obj followed by the rest of the arguments (@args). The subroutine should be defined in package "Class". If there is no subroutine foo in package ...
What is `git diff --patience` for?
...s in some cases.
Suppose you have the following file checked in to git:
.foo1 {
margin: 0;
}
.bar {
margin: 0;
}
Now we reorder the sections and add a new line:
.bar {
margin: 0;
}
.foo1 {
margin: 0;
color: green;
}
The default diff algorithm claims that the section head...
How to insert a newline in front of a pattern?
...ch is awkward, but it works:
$ sed 's/regexp/\
&/'
Example:
$ echo foo | sed 's/.*/\
&/'
foo
See here for details. If you want something slightly less awkward you could try using perl -pe with match groups instead of sed:
$ echo foo | perl -pe 's/(.*)/\n$1/'
foo
$1 refers to the ...
How to create a trie in Python
...current_dict[_end] = _end
... return root
...
>>> make_trie('foo', 'bar', 'baz', 'barz')
{'b': {'a': {'r': {'_end_': '_end_', 'z': {'_end_': '_end_'}},
'z': {'_end_': '_end_'}}},
'f': {'o': {'o': {'_end_': '_end_'}}}}
If you're not familiar with setdefault, it simply ...
How to forward declare a C++ template class?
...}
#include <iostream>
template <typename S, typename T>
void Foo (const std::vector<S,T> & vector)
{
std::cout << "do vector stuff, eg., display size = "
<< vector.size() << std::endl;
}
template <typename T>
void Foo (const T & t)
{
...
Why is the minimalist, example Haskell quicksort not a “true” quicksort?
...=)
(.&&) = liftM2 (&&)
-- ...
where doWhile cond foo = do
foo
b <- cond
when b $ doWhile cond foo
while cond foo = do
b <- cond
when b $ foo >> while cond foo
And here, a dumb test to see if it works.
...
Convert .pem to .crt and .key
...t: it consists of the DER format base64 encoded with additional header and footer lines. On input PKCS#8 format private keys are also accepted. The NET form is a format is described in the NOTES section.
-outform DER|NET|PEM
This specifies the output format, the options have the same meaning ...