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Can someone explain the traverse function in Haskell?
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traverse is the same as fmap, except that it also allows you to run effects while you're rebuilding the data structure.
Take a look at the example from the Data.Traversable documentation.
data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)
The Functor instance of Tr...
MySQL “incorrect string value” error when save unicode string in Django
...8mb4 uses 33% more space than utf-8 you'll need to make these fields 33% smaller.
In this case, change the max_length from 255 to 191.
Alternatively you can edit your MySQL configuration to remove this restriction but not without some django hackery
UPDATE: I just ran into this issue again and ...
Mysql - How to quit/exit from stored procedure
...e was no error, then use the accepted answer posted by @piotrm. Most typically, however, you will be bailing due to an error condition (especially in a SQL procedure).
As of MySQL v5.5 you can throw an exception. Negating exception handlers, etc. that will achieve the same result, but in a clean...
How to access data/data folder in Android device?
...'backup my data'. The resulting 'backup.ab' file on your computer contains all application data in android backup format. Basically it's a compressed tar file. This page explains how you can use OpenSSL's zlib command to uncompress it.
You can use the adb restore backup.db command to restore the b...
ReSharper - force curly braces around single line
...t to add the braces in the single-line scenario. And I had to set that in all six dropdowns under "Force Braces" to catch all the scenarios:
What I was really hoping for was to be able to set up ReSharper to do a yellow warning or red error when the rule was violated, but I haven't found a way t...
Setting an int to Infinity in C++
...or 2 147 483 647) if int is 32 bits wide on your implementation.
If you really need infinity, use a floating point number type, like float or double. You can then get infinity with:
double a = std::numeric_limits<double>::infinity();
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Django filter versus get for single object?
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get() is provided specifically for this case. Use it.
Option 2 is almost precisely how the get() method is actually implemented in Django, so there should be no "performance" difference (and the fact that you're thinking about it indicates you're vio...
using jquery $.ajax to call a PHP function
This may be a simple answer, but I'm using jQuery's $.ajax to call a PHP script. What I want to do is basically put that PHP script inside a function and call the PHP function from javascript.
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Changing Font Size For UITableView Section Headers
...wForHeaderInSection:(NSInteger)section {
UILabel *myLabel = [[UILabel alloc] init];
myLabel.frame = CGRectMake(20, 8, 320, 20);
myLabel.font = [UIFont boldSystemFontOfSize:18];
myLabel.text = [self tableView:tableView titleForHeaderInSection:section];
UIView *headerView = [[UIV...
How do I sort a vector of pairs based on the second element of the pair?
...response to your edits to your question, here's some thoughts ...
if you really wanna be creative and be able to reuse this concept a lot, just make a template:
template <class T1, class T2, class Pred = std::less<T2> >
struct sort_pair_second {
bool operator()(const std::pair<T1...