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How do the Proxy, Decorator, Adapter, and Bridge Patterns differ?
...ions.
Facade is a higher-level (read: simpler) interface to a subsystem of one or more classes. Suppose you have a complex concept that requires multiple objects to represent. Making changes to that set of objects is confusing, because you don't always know which object has the method you need to ca...
Split string into an array in Bash
...e over the elements:
for element in "${array[@]}"
do
echo "$element"
done
To get both the index and the value:
for index in "${!array[@]}"
do
echo "$index ${array[index]}"
done
The last example is useful because Bash arrays are sparse. In other words, you can delete an element or add a...
Callback when CSS3 transition finishes
...tect the end of a transition via jQuery:
$("#someSelector").bind("transitionend webkitTransitionEnd oTransitionEnd MSTransitionEnd", function(){ ... });
Mozilla has an excellent reference:
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Transitions/Using_CSS_transitions#Detecting_the_start_...
What does the exclamation mark do before the function?
... it turns it into an expression. It is now a function expression.
The ! alone doesn't invoke the function, of course, but we can now put () at the end: !function foo() {}() which has higher precedence than ! and instantly calls the function.
So what the author is doing is saving a byte per functio...
What are queues in jQuery?
...ns, reading the source and looking at examples helps me out tremendously. One of the best examples of a queue function I've seen is .delay():
$.fn.delay = function( time, type ) {
time = jQuery.fx ? jQuery.fx.speeds[time] || time : time;
type = type || "fx";
return this.queue( type, functio...
How does the main() method work in C?
...ultiple signatures for main, as well as variable-length argument lists, is one of those features.
Programmers noticed that they can pass extra arguments to a function, and nothing bad happens with their given compiler.
This is the case if the calling conventions are such that:
The calling functi...
How to find duplicates in 2 columns not 1
...t up a composite key between the two fields. This will require a unique stone_id and upcharge_title for each row.
As far as finding the existing duplicates try this:
select stone_id,
upcharge_title,
count(*)
from your_table
group by stone_id,
upcharge_title
having...
How to extract one column of a csv file
...
The simplest way I was able to get this done was to just use csvtool. I had other use cases as well to use csvtool and it can handle the quotes or delimiters appropriately if they appear within the column data itself.
csvtool format '%(2)\n' input.csv
Replacing 2...
When should I use semicolons in SQL Server?
...t have been introduced in recent years. (MERGE too for example). As mentioned in other answers, in the ANSI standard they are required
– Mark Sowul
Jul 28 '17 at 18:16
...
Computed / calculated / virtual / derived columns in PostgreSQL
...STORED
);
db<>fiddle here
VIRTUAL generated columns may come with one of the next iterations. (Not in Postgres 13, yet) .
Related:
Attribute notation for function call gives error
Until then, you can emulate VIRTUAL generated columns with a function using attribute notation (tbl.co...