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List changes unexpectedly after assignment. How do I clone or copy it to prevent this?
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With new_list = my_list, you don't actually have two lists. The assignment just copies the reference to the list, not the actual list, so both new_list and my_list refer to the same list after the assignment.
To actually copy the list, you have various possibilit...
What are the rules for the “…” token in the context of variadic templates?
...template parameter pack if it appears on the right side of an expression (call this expression pattern for a moment), or it's a pack argument if it appears on left side of the name:
...thing // pack : appears as template arguments
thing... // unpack : appears when consuming the arguments
The ru...
Why is early return slower than else?
...984281521812363]
>>> T(lambda : with_else()).repeat()
[0.36009842032996175, 0.28962249392031936, 0.2927151355828528]
>>> T(lambda : without_else(True)).repeat()
[0.31709728471076915, 0.3172671387005721, 0.3285821242644147]
>>> T(lambda : with_else(True)).repeat()
[0.309398...
What is the most efficient/elegant way to parse a flat table into a tree?
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Now that MySQL 8.0 supports recursive queries, we can say that all popular SQL databases support recursive queries in standard syntax.
WITH RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELECT m.* FROM MyTABLE AS m JOIN MyTree AS t ON m.ParentI...
How can I force Powershell to return an array when a call only returns one object?
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I actually feel like this is the most clear and safe option. You can reliably use ".Count - ge 1' on the collection or 'Foreach'
– Jaigene Kang
Jul 11 '17 at 22:24
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What's “wrong” with C++ wchar_t and wstrings? What are some alternatives to wide characters?
...e wchar_t is a distinct type whose values can represent distinct codes for all members of the largest extended character set specified among the supported locales (22.3.1).
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Is there a way to instantiate objects from a string holding their class name?
...initializing or assigning to it. Have a look at its documentation here. Finally, the use of a raw function pointer is also a bit oldish. Modern C++ code should be decoupled from specific functions / types. You may want to look into Boost.Function to look for a better way. It would look like this the...
How do I get around type erasure on Scala? Or, why can't I get the type parameter of my collections?
...hese instances are objects, you can pass them around, store them, and generally call methods on them. With the support of implicit parameters, it becomes a very powerful tool. Take the following example, for instance:
object Registry {
import scala.reflect.Manifest
private var map= Map.empty[...
JSON datetime between Python and JavaScript
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The lambda can be adapted to call the base implementation on non-datetime types, so TypeError can be raised if needed: dthandler = lambda obj: obj.isoformat() if isinstance(obj, datetime) else json.JSONEncoder().default(obj)
– Pascal...
How to open a new tab using Selenium WebDriver?
...ow. Obviously, you'd need to keep track of the window name(s) as normal to allow switching between them.
– Mark Rowlands
Jul 16 '13 at 15:42
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