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LINQ's Distinct() on a particular property
...the question). What I if want to use Distinct on a list of an Object on one or more properties of the object?
20 Answ...
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...
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...
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...
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 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...
Running a cron every 30 seconds
... not go down to sub-minute resolutions, you will need to find another way.
One possibility, though it's a bit of a kludge(a), is to have two jobs, one offset by 30 seconds:
# Need these to run on 30-sec boundaries, keep commands in sync.
* * * * * /path/to/executable param1 param2
* * *...
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...
Importing two classes with same name. How to handle?
...og4j.Logger and java.util.logging.Logger. Usually, I have no control over one side or the other; I'm doing legacy code integration.
– kevinarpe
Jul 1 '15 at 11:07
...
When to use static vs instantiated classes
... a life on its own)
(Yeah, I admit, really really overly-simplified...)
One thing about static methods/classes is that they don't facilitate unit testing (at least in PHP, but probably in other languages too).
Another thing about static data is that only one instance of it exists in your program...