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Virtual/pure virtual explained
What exactly does it mean if a function is defined as virtual and is that the same as pure virtual?
12 Answers
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Do the parentheses after the type name make a difference with new?
...e.
Sometimes the memory returned by the new operator will be initialized, and sometimes it won't depending on whether the type you're newing up is a POD (plain old data), or if it's a class that contains POD members and is using a compiler-generated default constructor.
In C++1998 there are 2 typ...
What is the correct JSON content type?
...been messing around with JSON for some time, just pushing it out as text and it hasn't hurt anybody (that I know of), but I'd like to start doing things properly.
...
How should I read a file line-by-line in Python?
...files faster than the garbage collector calls finalizers on orphaned file handles. The usual workaround is to trigger the GC immediately, but this is a nasty hack and it has to be done by every function that could encounter the error, including those in libraries. What a nightmare.
Or you could j...
how to exclude null values in array_agg like in string_agg using postgres?
... non_canonical_users
FROM groups g
GROUP BY g.id
) s
Or, simpler and may be cheaper, using array_to_string which eliminates nulls:
SELECT
g.id,
array_to_string(
array_agg(CASE WHEN g.canonical = 'Y' THEN g.users ELSE NULL END)
, ','
) canonical_users,
array...
Performance - Date.now() vs Date.getTime()
.../date it's been set to). That is, if you do this:
var now = new Date();
and then wait a while, a subsequent call to now.getTime() will tell the time at the point the variable was set.
share
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imp...
How to test an SQL Update statement before running it?
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In addition to using a transaction as Imad has said (which should be mandatory anyway) you can also do a sanity check which rows are affected by running a select using the same WHERE clause as the UPDATE.
So if you UPDATE is
UPDATE foo
SET bar = 42
WHERE col1 = 1
AND col2 = 'foobar';
...
Interface vs Base class
When should I use an interface and when should I use a base class?
38 Answers
38
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Are static fields open for garbage collection?
...ollected for garbage.
Check out the JLS Section 12.7 Unloading of Classes and Interfaces
A class or interface may be unloaded
if and only if its defining class
loader may be reclaimed by the garbage
collector [...] Classes and interfaces
loaded by the bootstrap loader may not
be unloa...
How does bash tab completion work?
I have been spending a lot of time in the shell lately and I'm wondering how the tab autocomplete works. What's the mechanism behind it? How does the bash know the contents of every directory?
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