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Use of alloc init instead of new
...selected ones are:
new doesn't support custom initializers (like initWithString)
alloc-init is more explicit than new
General opinion seems to be that you should use whatever you're comfortable with.
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What's wrong with nullable columns in composite primary keys?
...s version the "ext" part of the tuple is NOT NULL but defaults to an empty string -- which is semantically (and practically) different from a NULL. A NULL is an unknown, whereas an empty string is a deliberate record of "something not being present". In other words, "empty" and "null" are different ...
Check if a value is an object in JavaScript
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@Tresdin The best way is to run Object.prototype.toString.call(yourVar), being yourVar what you need to inspect. In case of arrays, Object.prototype.toString.call([1,2]) returns [object Array]
– Jose Rui Santos
Feb 25 '16 at 9:48
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Why should I use a pointer rather than the object itself?
...eir destructors called once they go out of scope. For example:
{
std::string s;
}
// s is destroyed here
On the other hand, if you use a pointer dynamically allocated, its destructor must be called manually. delete calls this destructor for you.
{
std::string* s = new std::string;
}
dele...
Difference between HashMap, LinkedHashMap and TreeMap
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private TreeMap<String ,Integer> mySection2 = new TreeMap<>(); mySection2.put("abc1", 2); mySection2.put("abc2",5); mySection2.put("abc3",3); ...
Extract month and year from a zoo::yearmon object
...an extract the date parts as required:
> format(date1, "%b") ## Month, char, abbreviated
[1] "Mar"
> format(date1, "%Y") ## Year with century
[1] "2012"
> format(date1, "%m") ## numeric month
[1] "03"
These are returned as characters. Where appropriate, wrap in as.numeric() if you want t...
How to drop rows of Pandas DataFrame whose value in a certain column is NaN
...ilippSchwarz This error occurs if the column (EPS in the example) contains strings or other types that cannot be digested by np.isfinite(). I recommend to use pandas.notnull() that will handle this more generously.
– normanius
Apr 5 '18 at 10:02
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Bash script to receive and repass quoted parameters
...# $4= "ddd ddd"
"$*" - quoted-dollar-star smashes the args into a single string (~1% of the time you actually want this behavior, eg in a conditional: if [[ -z "$*" ]]; then ...):
./quoted-dollar-star.sh aaa '' "'cc cc'" '"ddd ddd"'
# $1= aaa 'cc cc' "ddd ddd"
# $2=
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Return 0 if field is null in MySQL
...) returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
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How does IPython's magic %paste work?
...est_mode which allows you to copy paste example and test snippets from doc strings. This is also useful to execute interactive python session output that you could find in documentation and online forums, without having to first strip out the prompt strings.
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