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Why does Math.floor return a double?
...l to the argument and is equal to a mathematical integer". Given a value x > 2^53 that will not be the same as the value with its fractional part truncated. It may well be quite a bit smaller than that.
– Jim Garrison
Sep 5 '16 at 20:10
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Overloading Macro on Number of Arguments
...OO2)(__VA_ARGS__)
So if you have these macros:
FOO(World, !) # expands to FOO2(World, !)
FOO(foo,bar,baz) # expands to FOO3(foo,bar,baz)
If you want a fourth one:
#define GET_MACRO(_1,_2,_3,_4,NAME,...) NAME
#define FOO(...) GET_MACRO(__VA_ARGS__, FOO4, FOO3, FOO2)(__VA_ARGS__)
F...
How can I implement prepend and append with regular JavaScript?
...ild)
Inserts the node newChild as a child of parentNode before the
existing child node refChild. (Returns newChild.)
If refChild is null, newChild is added at the end of the list of
children. Equivalently, and more readably, use
parentNode.appendChild(newChild).
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JPA EntityManager: Why use persist() over merge()?
EntityManager.merge() can insert new objects and update existing ones.
15 Answers
15
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Why wasn't PyPy included in standard Python?
...true of all "pure GC" strategies.
PyPy does not yet fully support Python 3.x, although that is an active work item.
PyPy is a great project, but runtime speed on CPU-intensive tasks isn't everything, and in many applications it's the least of many concerns. For instance, Django can run on PyPy an...
How do I sort an observable collection?
...g an observable and returning the same object sorted can be done using an extension method. For larger collections watch out for the number of collection changed notifications.
I have updated my code to improve performance (thanks to nawfal) and to handle duplicates which no other answers here do at...
How to display full (non-truncated) dataframe information in html when converting from pandas datafr
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Set the display.max_colwidth option to -1:
pd.set_option('display.max_colwidth', -1)
set_option docs
For example, in iPython, we see that the information is truncated to 50 characters. Anything in excess is ellipsized:
If you set the display...
How many parameters are too many? [closed]
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162
votes
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Cartesian product of multiple arrays in JavaScript
...overly complicated, most of them take 20 lines of code or even more.
This example uses just two lines of vanilla JavaScript, no lodash, underscore or other libraries:
let f = (a, b) => [].concat(...a.map(a => b.map(b => [].concat(a, b))));
let cartesian = (a, b, ...c) => b ? cartesian(f(...
Pandas dataframe get first row of each group
...If you need id as column:
>>> df.groupby('id').first().reset_index()
id value
0 1 first
1 2 first
2 3 first
3 4 second
4 5 first
5 6 first
6 7 fourth
To get n first records, you can use head():
>>> df.groupby('id').head(2).reset_index(drop=True)
...