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Why is Scala's immutable Set not covariant in its type?
...ameter of type A due to the contravariance of functions. Set could potentially be contravariant in A, but this too causes issues when you want to do things like this:
def elements: Iterable[A]
In short, the best solution is to keep things invariant, even for the immutable data structure. You'll...
How to delete migration files in Rails 3
...
I usually:
Perform a rake db:migrate VERSION=XXX on all environments, to the version before the one I want to delete.
Delete the migration file manually.
If there are pending migrations (i.e., the migration I removed was not the...
✔ Checkmark selected row in UITableViewCell
...
Update Swift 4
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
tableView.cellForRow(at: indexPath)?.accessoryType = .checkmark
}
func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPat...
Get current time in milliseconds in Python?
...illis = int(round(time.time() * 1000))
print millis
Quick'n'easy. Thanks all, sorry for the brain fart.
For reuse:
import time
current_milli_time = lambda: int(round(time.time() * 1000))
Then:
>>> current_milli_time()
1378761833768
...
Best way to handle list.index(might-not-exist) in python?
...thonic solution is to use only try/except and not the -1 sentinel value at all. I.E. you should rewrite otherfunction. On the other hand, if it ain't broke, ...
– Andrew Jaffe
Jan 25 '10 at 15:49
...
Python argparse: default value or specified value
...
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--example', nargs='?', const=1, type=int)
args = parser.parse_args()
print(args)
% test.py
Namespace(example=None)
% test.py --example
Namespace(example=1)
% test.py --example 2
Namespace(example=2)
nargs...
Check if URL has certain string with PHP
...URL and the rest check if it contains the word "car".
$url = 'http://' . $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
if (strpos($url,'car') !== false) {
echo 'Car exists.';
} else {
echo 'No cars.';
}
shar...
Global access to Rake DSL methods is deprecated
...
You can "delete" Rake 0.9.1 by running the following command:
gem uninstall rake -v=0.9.1
If you have multiple versions of the gem installed, you'll be prompted to pick a version.
After 0.9.1 was cleaned out, I ran
bundle update rake
and was finally able to create my database files. I was ...
Mysql: Select rows from a table that are not in another
How to select all rows in one table that do not appear on another?
8 Answers
8
...
Cast Object to Generic Type for returning
...> T convertInstanceOfObject(java.lang.Object);
Code:
0: aload_0
1: areturn
2: astore_1
3: aconst_null
4: areturn
Exception table:
from to target type
0 1 2 Class java/lang/ClassCastException
public static void main(java...