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Pragma in define macro
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If you're using c99 or c++0x there is the pragma operator, used as
_Pragma("argument")
which is equivalent to
#pragma argument
except it can be used in macros (see section 6.10.9 of the c99 standard, or 16.9 of the c++0x final committee draft)
For example,
#define STRINGIFY(a) #a
#def...
How can I use “sizeof” in a preprocessor macro?
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Following snippets will produce no code if sizeof(someThing) equals PAGE_SIZE; otherwise they will produce a compile-time error.
1. C11 way
Starting with C11 you can use static_assert (requires #include <assert.h>).
Usage:
static_assert(sizeof(someThing) == PAGE_SIZE, "Data structure do...
How do I read any request header in PHP
...instead of all headers, the quickest method is:
<?php
// Replace XXXXXX_XXXX with the name of the header you need in UPPERCASE (and with '-' replaced by '_')
$headerStringValue = $_SERVER['HTTP_XXXXXX_XXXX'];
ELSE IF: you run PHP as an Apache module or, as of PHP 5.4, using FastCGI (simple me...
Add a prefix to all Flask routes
... that you are going to run this application inside of a WSGI container (mod_wsgi, uwsgi, gunicorn, etc); you need to actually mount, at that prefix the application as a sub-part of that WSGI container (anything that speaks WSGI will do) and to set your APPLICATION_ROOT config value to your prefix:
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Javascript replace with reference to matched group?
I have a string, such as hello _there_ . I'd like to replace the two underscores with <div> and </div> respectively, using JavaScript . The output would (therefore) look like hello <div>there</div> . The string might contain multiple pairs of underscores.
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How to change the CHARACTER SET (and COLLATION) throughout a database?
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change database collation:
ALTER DATABASE <database_name> CHARACTER SET utf8 COLLATE utf8mb4_0900_ai_ci;
change table collation:
ALTER TABLE <table_name> CONVERT TO CHARACTER SET utf8 COLLATE utf8mb4_0900_ai_ci;
change column collation:
ALTER TABLE <table_name&g...
How to convert list of tuples to multiple lists?
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xs, ys = [x for x, y in zs], [y for x, y in zs]
return xs, ys
if __name__ == '__main__':
from timeit import timeit
setup_string='''\
N = 2000000
xs = list(range(1, N))
ys = list(range(N+1, N*2))
zs = list(zip(xs, ys))
from __main__ import t1, t2, t3
'''
print(f'zip:\t\t{timeit(...
Passing variable number of arguments around
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To pass the ellipses on, you have to convert them to a va_list and use that va_list in your second function. Specifically;
void format_string(char *fmt,va_list argptr, char *formatted_string);
void debug_print(int dbg_lvl, char *fmt, ...)
{
char formatted_string[MAX_FMT_SI...
Best way to allow plugins for a PHP application
...try point for plugins */
function hook() {
global $listeners;
$num_args = func_num_args();
$args = func_get_args();
if($num_args < 2)
trigger_error("Insufficient arguments", E_USER_ERROR);
// Hook name should always be first argument
$hook_name = array_shift($ar...
Elegant way to invert a map in Scala
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Assuming values are unique, this works:
(Map() ++ origMap.map(_.swap))
On Scala 2.8, however, it's easier:
origMap.map(_.swap)
Being able to do that is part of the reason why Scala 2.8 has a new collection library.
...