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Creating a singleton in Python
...
class Foo(object):
pass
some_global_variable = Foo()
Modules are imported only once, everything else is overthinking. Don't use singletons and try not to use globals.
...
In-place edits with sed on OS X
...native way is to use built-in substitution in Vim Ex mode, like:
$ ex +%s/foo/bar/g -scwq file.txt
and for multiple-files:
$ ex +'bufdo!%s/foo/bar/g' -scxa *.*
To edit all files recursively you can use **/*.* if shell supports that (enable by shopt -s globstar).
Another way is to use gawk a...
MySQL/SQL: Group by date only on a Datetime column
...
Cast the datetime to a date, then GROUP BY using this syntax:
SELECT SUM(foo), DATE(mydate) FROM a_table GROUP BY DATE(a_table.mydate);
Or you can GROUP BY the alias as @orlandu63 suggested:
SELECT SUM(foo), DATE(mydate) DateOnly FROM a_table GROUP BY DateOnly;
Though I don't think it'll make...
How to get label of select option with jQuery?
...layed text for both styles of <option> elements:
<option label="foo"><option> -> "foo"
<option>bar<option> -> "bar"
If it has both a label attribute and text inside the element, it'll use the label attribute, which is the same behavior as the browser.
For pos...
Reference: Comparing PHP's print and echo
...equence:
<?php
function bar( $baz ) {
// other code
}
function foo() {
return print("In and out ...\n");
}
if ( foo() ) {
bar();
}
You might find print of particular value when it comes to debugging on the fly, as the next example illustrates:
<?php
$haystack = 'abcde';
$n...
How to write a Ruby switch statement (case…when) with regex and backreferences?
...egex matching groups are always stored in pseudo variables $1 to $9:
case foo
when /^([0-9][0-9])/
print "the month is #{$1}"
else
print "something else"
end
You can also use the $LAST_MATCH_INFO pseudo variable to get at the whole MatchData object. This can be useful when using named cap...
Cross compile Go on OSX?
...quivalent. While in some other Shell, e.g. FISH shell, it does not support FOO=bar cmd, so you have to use env FOO=bar cmd. Thus I think the biggest advantage to use env FOO=bar cmd is compatibility.
– PickBoy
Dec 1 '16 at 12:12
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Why is it impossible to build a compiler that can determine if a C++ function will change the value
...able (or halt) for every possible function.
Here's an easy example:
void foo() {
if (bar() == 0) this->a = 1;
}
How can a compiler determine, just from looking at that code, whether foo will ever change a? Whether it does or doesn't depends on conditions external to the function, namely t...
Dual emission of constructor symbols
...e Itanium C++ ABI.
According to the ABI, the mangled name for your Thing::foo() is easily parsed:
_Z | N | 5Thing | 3foo | E | v
prefix | nested | `Thing` | `foo`| end nested | parameters: `void`
You can read the constructor names similarly, as below. Notice how the constructor ...
Is there a MySQL command to convert a string to lowercase?
...
SELECT LOWER(foo) AS foo FROM bar
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