All Questions
2,211,585
questions
794
votes
13
answers
320k
views
When to use single quotes, double quotes, and backticks in MySQL
I am trying to learn the best way to write queries. I also understand the importance of being consistent. Until now, I have randomly used single quotes, double quotes, and backticks without any real ...
- 27.5k
175
votes
2
answers
28k
views
What is a debugger and how can it help me diagnose problems?
This is intended to be a general-purpose question to assist new programmers who have a problem with a program, but who do not know how to use a debugger to diagnose the cause of the problem.
This ...
- 48k
2317
votes
32
answers
478k
views
How do you parse and process HTML/XML in PHP?
How can one parse HTML/XML and extract information from it?
234
votes
3
answers
42k
views
How to use ThreeTenABP in Android Project
I'm using Android Studio 2.1.2 and my Java setup is the following:
>java -version
> openjdk version "1.8.0_91"
> OpenJDK Runtime Environment (build 1.8.0_91-8u91-b14-3ubuntu1~15.10....
- 6,675
695
votes
5
answers
99k
views
Why is iostream::eof inside a loop condition (i.e. `while (!stream.eof())`) considered wrong?
I just found a comment in this answer saying that using iostream::eof in a loop condition is "almost certainly wrong". I generally use something like while(cin>>n) - which I guess implicitly ...
- 26.5k
556
votes
18
answers
269k
views
How do I create variable variables?
I know that some other languages, such as PHP, support a concept of "variable variable names" - that is, the contents of a string can be used as part of a variable name.
I heard that this is ...
Pyornide
760
votes
22
answers
1.1m
views
Asking the user for input until they give a valid response
I am writing a program that accepts user input.
#note: Python 2.7 users should use `raw_input`, the equivalent of 3.X's `input`
age = int(input("Please enter your age: "))
if age >= 18:
...
849
votes
31
answers
569k
views
How to test multiple variables for equality against a single value?
I'm trying to make a function that will compare multiple variables to an integer and output a string of three letters. I was wondering if there was a way to translate this into Python. So say:
x = 0
y ...
- 8,681
680
votes
6
answers
297k
views
Why is “while( !feof(file) )” always wrong?
What is wrong with using feof() to control a read loop? For example:
#include <stdio.h>
#include <stdlib.h>
int
main(int argc, char **argv)
{
char *path = "stdin";
FILE ...
- 210k
572
votes
3
answers
58k
views
What is the difference between client-side and server-side programming?
I have this code:
<script type="text/javascript">
var foo = 'bar';
<?php
file_put_contents('foo.txt', ' + foo + ');
?>
var baz = <?php echo 42; ?>;
...
- 518k
2540
votes
8
answers
387k
views
What is The Rule of Three?
What does copying an object mean?
What are the copy constructor and the copy assignment operator?
When do I need to declare them myself?
How can I prevent my objects from being copied?
- 261k
957
votes
19
answers
80k
views
List of lists changes reflected across sublists unexpectedly
I created a list of lists:
>>> xs = [[1] * 4] * 3
>>> print(xs)
[[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]
Then, I changed one of the innermost values:
>>> xs[0][0] = 5
>...
- 19.9k
361
votes
25
answers
1.0m
views
What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?
What does ArrayIndexOutOfBoundsException mean and how do I get rid of it?
Here is a code sample that triggers the exception:
String[] names = { "tom", "bob", "harry" };
for (int i = 0; i <= ...
- 11.6k
1496
votes
22
answers
468k
views
How does the "this" keyword work, and when should it be used?
I am looking to find a clear explanation of what the "this" keyword does, and how to use it correctly.
It seems to behave strangely, and I don't fully understand why.
How does this work and ...
- 46.8k
4611
votes
38
answers
3.1m
views
How slicing in Python works
How does Python's slice notation work? That is: when I write code like a[x:y:z], a[:], a[::2] etc., how can I understand which elements end up in the slice?
See Why are slice and range upper-bound ...
- 80.1k