A **loop** is a sequence of statements which is specified once but which may be carried out several times in succession.
7
votes
7answers
481 views
provability of while loop vs for loop
I have this teacher, he's quite smart (sometimes, haha) he said good programmers try to use while loops instead of for loops. the reason he gave for this is because while loops can be proven, as in, ...
-2
votes
0answers
30 views
Using Operations on a List in Python and Aggregating Results in New List [migrated]
I have a list of numbers, all of which need to be divided by the same number. I can do this, no problem, but how do I create a new list featuring these new quotients?
I have tried:
for n in numbers:
...
0
votes
1answer
51 views
Sorting Sentences by New Words in Each
A very useful learning tool I stumbled across for Chinese was a massive list of sentences that, barring the first 10 or 15, only differed by the ones before by one or two words, or at least as few as ...
-2
votes
0answers
67 views
JavaScript prototype chain probable infinite cycle lookup [migrated]
I have a query regarding JavaScript object prototype chains. Suppose I create an Object
var first = { a: 1};var second = Object.create(first);
Now I know that if I look up for the attribute a on ...
1
vote
1answer
92 views
adding the digits of a number
I am trying to write a program that asks the user for a decimal number and then calculates the sum of its digits. for example if the number is 123.25 then the sum will be 1+2+3+2+5=13.
I decided to ...
2
votes
3answers
199 views
The recommended Way to exit a Loop
Occasionally - but recurringly - I face the following loop pattern problem:
CodeSnippet1
DO WHILE LoopCondition //LoopCondition depends on some pre-calculation from CodeSnippet1
CodeSnippet2 ...
2
votes
1answer
34 views
Comparing path strings against list of rules
I am trying to find a way to enhance a filtering algorithm. I am developing a backup software that enables users to specify custom filters to exclude unwanted files/directories.
Currently when trying ...
0
votes
1answer
82 views
Most efficient way to calculate number of iterations to run
Let's say I have a batch process that executes 4 times per loop, and needs to execute a total of 9 items.
Example:
Iteration 1 executes 4 items of 9, leaving 5 left
Iteration 2 executes 4 times of ...
2
votes
0answers
63 views
Loop Unfolding and Named Significant Bits
I've been writing a Parser Compiler for the last seven or so years, and I recently got to the point (yet again, never satisfied) of structuring the portion dealing with the portions of the language ...
-3
votes
3answers
159 views
Real life scenario of why we would use loops [closed]
I am going to school to become a programmer, and I am doing some homework and I have a question. It wants me to give an example of why we would use loops in the real world. And I was thinking about ...
2
votes
1answer
94 views
Proper way to refactor multiple if based conditions [duplicate]
I took over a large legacy code base. It has a code like this:
if ($route == 'login' || $route == 'logout' || $route == 'forgot-password') {
return;
}
if ($loggedInUser == false && ...
0
votes
4answers
218 views
How to prove that this while loop calculates n^2
I'm studying for my exam of logic later this week and I have to prove that this while loop:
i := 0
s := 0
while i < n do
i := i + 1
s := s + (2*i -1)
calculates n^2. This question is ...
8
votes
5answers
1k views
How to structure a loop that repeats until success and handles failures
I am a self-taught programmer. I started programming about 1.5 years ago. Now I have started to have programming classes in school. We have had programming classes for 1/2 year and will have another ...
4
votes
5answers
1k views
Are there real-life usage and applications for “do while” loops? [closed]
When I see for and while loops all over production codes and mammoth projects, the last time I saw a do while loop is for a university assignment involving menu-based console input program. About 50 ...
1
vote
3answers
85 views
Using higher order functions to apply m out of M filter's and then transform data of size n?
Total no: of filters possible is M . User can select m filters where m <= M . A typical example is files from a folder , he could say modified between so and so date , start with so and so and so ...
4
votes
1answer
199 views
Functional programming for loop side effect
I am trying to get my head around as to why having a local variable or a for loop inside a function is not considered to be pure functional programming.
Given this function:
int as_int(char *str)
{
...
1
vote
3answers
135 views
Use of for loop conditional statement unrelated to iterating variable
Is it considered decent form to write code like this:
int done = 0;
for (x = 0; !done; x++) {
... something involving 'x', that might end early ...
if (!(x < max))
done = 1;
}
...
0
votes
1answer
61 views
How can I iterate over two loops of mismatched sizes, keeping them in sync?
I have a database table in which each row is one movie (with fields like 'title', 'director' and 'writer'), and a related table where each row is one screenshot from a movie (with the fields ...
4
votes
2answers
306 views
Loop runtime question
I had an exam today and I feel that I did pretty well, except I could not for the life of me figure out what appears to be an unbelievably simple question.
We were asked to give theta notation run ...
-4
votes
4answers
223 views
Why are for loops needed? [duplicate]
It seems to me that a while loop with the appropriate break statements can replace them entirely. I understand that a break statement may not feel as "smooth" as a for loop that does something a ...
1
vote
2answers
435 views
Infinite while loop CPU usage
I'm coding an script in C, which is going to check constantly an array of events, the idea is to check if the Date and time of certain event is equal to de current time and trigger something, i'm ...
5
votes
2answers
413 views
Why do some programming languages have break statements, but not higher-order break statements? [closed]
I may have been exposed to exactly the wrong languages, but though many have loops and break statements, none of the languages I am familiar with have higher-order break statements¹. While a regular ...
37
votes
2answers
4k views
How do I move away from the “for-loop” school of thought?
This is a rather conceptual question, but I was hoping I could get some good advice on this. A lot of the programming I do is with (NumPy) arrays; I often have to match items in two or more arrays ...
-1
votes
1answer
100 views
Finding “spare time” in a day from within a list of events
I have a list of events which is always sorted chronologically. The start time is always followed by the end time. Times are strings formatted as 'HHmmss'.
// list of events
var events = [
...
0
votes
1answer
111 views
comparison of an unsigned variable to 0
When I execute the following loop :
unsigned m;
for( m = 10; m >= 0; --m ){
printf("%d\n",m);
}
the loop doesn't stop at m==0, it keeps executing interminably, so I thought that ...
0
votes
1answer
177 views
Python case statement? [duplicate]
I made a simple Python script that takes user input in order to generate a series of mathematical responses. In one part I did this:
while True:
And iterated through the loop until I used an if ...
98
votes
8answers
15k views
Why is polling accepted in web programming?
I am currently working on a Ruby on Rails project which shows a list of images.
A must-have for this project is that it shows new posts in realtime without the need of refreshing the web page. After ...
1
vote
2answers
726 views
Is “continue” and “break” in loops antipattern/bad practice in Java? [duplicate]
I see the main purpose of continue in programming, it can get you out from the rest of loop steps like:
while(condition1){
... code ...
if(!condition2){
continue;
}
... code ...
...
3
votes
4answers
257 views
Indefinite loops where the first time is different
This isn't a serious problem or anything someone has asked me to do, just a seemingly simple thing that I came up with as a mental exercise but has stumped me and which I feel that I should know the ...
2
votes
3answers
3k views
What are the differences between a while loop and a for loop?
What are the differences between a while loop and a for loop? It seems to me that they are the same.
0
votes
2answers
4k views
foreach in list or foreach in list.where [duplicate]
I don't know what to call this question.
This is my example:
foreach (var item in lstItem.Where(item => stock.ItemCode == item.ItemCode))
{
stock.ItemName = item.ItemName;
...
1
vote
1answer
242 views
Is there a purely SQL alternate to looping?
Historically, I probably would have written a script (php or something) to loop through all spreadsheet rows and perform some calculations.
I'm looking for a pure SQL solution on the presumption ...
0
votes
0answers
56 views
Where should I declare variables used in for-loops in Java for maximum efficiency? [duplicate]
I'm talking hypothetically but I'll use an example of what I worked on in a programming class a while ago. There's a better way to actually perform the operation, but that's not the point.
An example ...
7
votes
5answers
438 views
Is doing an assignment inside a condition considered a code smell?
Many times I have to write a loop that requires initialization of a loop condition, and an update every time the loop executes. Here's one example:
List<String> currentStrings = ...
2
votes
2answers
209 views
Is there a difference between declaring variables outside or inside a loop? [closed]
Is there any difference if I were to write something like this:
int row,col;
for(row = 0; row < data.length; row++){
for(col = 0; col < data[row].length;col++){
//do ...
3
votes
2answers
219 views
'Game loop' in a non-game application?
In real-time games, there is always a game loop that runs every few milliseconds, updates the game with new data and repaints the entire screen.
Is this something that is seen in other types of ...
-2
votes
4answers
295 views
Are for loops supposed to be read inward or outward? [closed]
for (i = 0; i < 3; i++)
{
for (j = 0; j < 4; j++)
{
cout << arr2d[i][j] << "\t";
}
cout << endl;
.....
Like that for example. Do you read ...
2
votes
4answers
3k views
Complexity in nested loops
Foreword:
In this post, I will make the common confusion between O(n) and Theta(n) as complexity notations.
I will write pseudo-code to talk about algorithms, using whatever notation I find to my ...
6
votes
3answers
639 views
Is doing two things on one line always a bad practice?
int *itPins = pins;
for(int i = 0; i < count; i++)
{
ConfigureGpifPinAsGpioOutput(itPins);
itPins++;
}
I have the impression that doing two things in one line is bad practice. This is why ...
0
votes
2answers
222 views
Is there a special name for a condition which will break a loop if it increments a set number of times
Is there a name for including a limitation in a loop structure to prevent it from running if its primary condition becomes unwieldy.
For example
for (var i = 0; i < len; i++){
...
4
votes
1answer
390 views
Will loop constructs become obsolete? [closed]
By loop constructs I mean for… and while… constructs with nested statements.
Currently I am coding a tool in Python and decided out of curiosity not to use the regular loops - and rely on ...
1
vote
3answers
329 views
How do you avoid looping mistakes? Mistakes that are not detected by systems [closed]
I had this crazy initialisation --
documentList = new ArrayList<Map<String,Integer>>();
which I intended to store a new map everytime in a loop but unfortunately put itself inside the ...
1
vote
1answer
179 views
Randomly and uniquely iterating over a range
Say you have a range of values (or anything else) and you want to iterate over the range and stop at some indeterminate point.
Because the stopping value could be anywhere in the range, iterating ...
3
votes
5answers
585 views
What does the English word “for” exactly mean in “for” loops?
English is not my first language, but since the keywords in programming languages are English words, I usually find it easy to read source code as English sentences:
if (x > 10) f(); => "If ...
0
votes
10answers
982 views
Why does the instruction “do” require a “while”? [closed]
Since this statement is so common:
while (true) (Java)
or
while (1) (C)
or sometimes
for (;;)
Why is there not a single instruction for this? I could think that an instruction that could do it ...
0
votes
2answers
435 views
Best Practice - Loop Exit Via Iterator Modification
I had an interesting discussion with my boss today regarding exiting a loop before the terminal condition is met. He had a construct in some of his VB6 code that looked something like this:
Dim ...
0
votes
1answer
85 views
Code execution within delimiters
Is there any way I can execute a block of code in a loop, like so:
[ some code goes here ]
Where the delimiters are "[" and "]", and also allowing for nested blocks, i.e.:
[the user can create ...
0
votes
2answers
168 views
Loading chunks around center
I am making a voxel game like Minecraft. I am able to load chunks using multithreading with the code...
for (int x = 0; x < WorldSettings.WORLD_WIDTH_IN_CHUNKS; x++)
{
for (int y = 0; y < ...
16
votes
4answers
13k views
Why are nested loops considered bad practice?
My lecturer mentioned today that it was possible to "label" loops in Java so that you could refer to them when dealing with nested loops. So I looked up the feature as I didn't know about it and many ...
6
votes
4answers
1k views
Is it a performance hit to create threads that loop a lot to check for things?
This is a generic question that I've always wondered.
In general, is it intensive for a CPU to create threads that perform "while not true ..." loops or similar?
For example, suppose I do:
// ...
