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What is the most efficient/elegant way to parse a flat table into a tree?
...r_id = 1
ORDER BY f.name;
Re comment from @Nate:
SELECT f.name, GROUP_CONCAT(b.ancestor_id order by b.path_length desc) AS breadcrumbs
FROM FlatTable f
JOIN ClosureTable a ON (f.id = a.descendant_id)
JOIN ClosureTable b ON (b.descendant_id = a.descendant_id)
WHERE a.ancestor_id = 1
GROUP BY...
Why do pthreads’ condition variable functions require a mutex?
...pthread_cond_wait(&cond); //imagine cond_wait did not have a mutex
char *data = some_data;
some_data = NULL;
handle(data);
}
you'd naturally get a lot of race condition, what if the other thread did some_data = new_data right after you got woken up, but before you did data = some_d...
Difference between 'new operator' and 'operator new'?
...ething like your own container, you can call operator new directly, like:
char *x = static_cast<char *>(operator new(100));
It's also possible to overload operator new either globally, or for a specific class. IIRC, the signature is:
void *operator new(size_t);
Of course, if you overloa...
Why does String.split need pipe delimiter to be escaped?
...ring "\\|" means the regular expression '\|' which means match exactly the character '|'.
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PHP validation/regex for URL
...
Some things that jump out at me: use of alternation where character classes are called for (every alternative matches exactly one character); and the replacement shouldn't have needed the outer double-quotes (they were only needed because of the pointless /e modifier on the regex).
...
What does the ??!??! operator do in C?
...otnote 12 (h/t @Random832):
The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
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How to read a single character from the user?
Is there a way of reading one single character from the user input? For instance, they press one key at the terminal and it is returned (sort of like getch() ). I know there's a function in Windows for it, but I'd like something that is cross-platform.
...
Getting a list of files in a directory with a glob
...ing like that.
NSMutableArray* files = [NSMutableArray array];
glob_t gt;
char* pattern = "/bin/*";
if (glob(pattern, 0, NULL, &gt) == 0) {
int i;
for (i=0; i<gt.gl_matchc; i++) {
[files addObject: [NSString stringWithCString: gt.gl_pathv[i]]];
}
}
globfree(&gt);
retu...
Why can't Python's raw string literals end with a single backslash?
...string; for example, r"\"" is a
valid string literal consisting of two
characters: a backslash and a double
quote; r"\" is not a valid string
literal (even a raw string cannot end
in an odd number of backslashes).
Specifically, a raw string cannot end
in a single backslash (since the
...
How can I echo a newline in a batch file?
...
@quetzalcoatl, it gets even stranger. Other characters besides dot work too. SS64 says better syntax is echo( for improved performance (still with no space mind you). Extended discussion of other characters and their merits/flaws at ECHO. FAILS to give text or blank ...