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What is the copy-and-swap idiom?
...s arguably the most nuanced and difficult. How should it be done? What pitfalls need to be avoided?
The copy-and-swap idiom is the solution, and elegantly assists the assignment operator in achieving two things: avoiding code duplication, and providing a strong exception guarantee.
How does it wor...
How can I use threading in Python?
...ticle/blog post that you should definitely check out (no affiliation) - Parallelism in one line: A Better Model for Day to Day Threading Tasks. I'll summarize below - it ends up being just a few lines of code:
from multiprocessing.dummy import Pool as ThreadPool
pool = ThreadPool(4)
results = pool.m...
ArrayList initialization equivalent to array initialization [duplicate]
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The selected answer is: ArrayList<Integer>(Arrays.asList(1,2,3,5,8,13,21));
However, its important to understand the selected answer internally copies the elements several times before creating the final array, and that th...
Getting list of parameter names inside python function [duplicate]
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Well we don't actually need inspect here.
>>> func = lambda x, y: (x, y)
>>>
>>> func.__code__.co_argcount
2
>>> func.__code__.co_varnames
('x', 'y')
>>>
>>> def func2(x,y=3):
... print(...
Change a Git remote HEAD to point to something besides master
...inking about these specific services.
Now they have a drop-down menu for selecting the HEAD branch at http://repo.or.cz (example: http://repo.or.cz/editproj.cgi?name=for-me-and-for-all_imz.git);
and at http://gitorious.org, too (look somewhere in the settings);
and at http://GitHub.com: admin >...
SQL Server Management Studio won't let me add an index to a table
...l I had to do was close the Table Designer and right-click on the Index to select "Properties" in order to add/edit them.... All these years wasted on writing custom scripts. face-palm I want my youth back!
– MikeTeeVee
Nov 17 '15 at 19:55
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Why dict.get(key) instead of dict[key]?
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It allows you to provide a default value if the key is missing:
dictionary.get("bogus", default_value)
returns default_value (whatever you choose it to be), whereas
dictionary["bogus"]
would raise a KeyError.
If omitted...
GROUP_CONCAT ORDER BY
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You can use ORDER BY inside the GROUP_CONCAT function in this way:
SELECT li.client_id, group_concat(li.percentage ORDER BY li.views ASC) AS views,
group_concat(li.percentage ORDER BY li.percentage ASC)
FROM li GROUP BY client_id
...
How to execute XPath one-liners from shell?
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You should try these tools :
xmlstarlet : can edit, select, transform... Not installed by default, xpath1
xmllint : often installed by default with libxml2-utils, xpath1 (check my wrapper to have --xpath switch on very old releases and newlines delimited output (v < 2.9.9)
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How to set child process' environment variable in Makefile
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I have GNU make 3.81, and all: <\n\t>export PROJ_ROOT=$(CURDIR)<\n\t>echo $(PROJ_ROOT)<\n> outputs the correct expansion for the first row, but only echo for the second one. PROJ_ROOT is not set after running make. Spaces around = gi...