A **loop** is a sequence of statements which is specified once but which may be carried out several times in succession.

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-3
votes
3answers
89 views

Best way to handle variables used in a for loop? [duplicate]

From previous experience, I had always thought that, if you are going to use variables inside of a for loop, it was much better to declare them outside of the loop vs. inside the loop itself. I ...
20
votes
8answers
3k views

At what point is it taboo to have loops within loops?

Just curious. The most I have ever had was a for loop within a for loop, because after reading this from Linus Torvalds: Tabs are 8 characters, and thus indentations are also 8 characters. There ...
14
votes
2answers
1k views

Filtering foreach loops with a where condition vs continue guard clauses

I've seen some programmers use this: foreach (var item in items) { if (item.Field != null) continue; if (item.State != ItemStates.Deleted) continue; // code } instead ...
108
votes
11answers
12k views

Is there anything that can be done with recursion that can't be done with loops?

There are times where using recursion is better than using a loop, and times where using a loop is better than using recursion. Choosing the "right" one can save resources and/or result in fewer lines ...
-1
votes
1answer
167 views

eradicating the array = loop mindset [closed]

I have noticed a common issue in code reviews, that takes this form: // "arr" is an array for (i = 0; i < arr.length; ++i) { if (i == 3) { // do something with arr[i] } if (i ...
6
votes
2answers
2k views

Is using for loop syntax for a “with(variable)” block an anti-pattern?

I fooled around with for-loops, remembered the with keyword from delphi and came up with following pattern (defined as a live template in IntelliJ IDEA): for ($TYPE$ $VAR$ = $VALUE$; $VAR$ != null; ...
2
votes
2answers
131 views

Did labelled loops pre-date for loops?

Was the first implementation of looping control flow effectively the goto (or something like a labelled JMP in assembler) or was there another syntactic construction? for (für) was introduced in ...
0
votes
0answers
64 views

Is there a school of thought where while(1) or while (true) is a code smell? [duplicate]

My employer requires code reviews for all devs, and new employees are required to to have their code reviewed by a senior dev. Initially, trainees get to pick a small project they are working on and ...
0
votes
1answer
100 views

Code readability on non-trivial loop variables [closed]

My co-worker and I discussing about the code readability on simple loops. Suppose a method takes an integer parameter and does some operation on the elements of an array depending on the parameter. ...
-2
votes
2answers
74 views

Find index of string in an array of strings where overlap could occur

I am having some trouble writing a variant of sub-string search. Essentially the goal is to write a method that can perform sub-string search except that the source data is in an array of Strings ...
0
votes
2answers
116 views

Refactoring method with nested loops and 6 variables [duplicate]

I have a method which implements a small section of a (complex) algorithm. This algorithm has taken me several weeks to perfect and is by far the fastest method I can find. The method in question has ...
3
votes
2answers
615 views

Using 'reduce' vs 'for' loop for returning boolean [closed]

I was wondering what people think about using a reduce function vs loop for returning true if a condition exists. Example: var a = [1, 5, 7, 4, 2, 5, 3]; var greaterThan5 = a.reduce(function(prev, ...
1
vote
2answers
87 views

Factored out loop control in Python

I have a for loop in python like this: for item in items: onwards = make_flow_decision(item) if onwards == 'break': break elif onwards == 'continue': continue elif ...
3
votes
2answers
145 views

Handling exceptions in a loop without breaking the loop (try to process all members)

Scenario: I have a loop that iterates over an Array of COM objects and does some work using them. My fear, working with COM objects, is that some exception will creep up (possibly on another ...
0
votes
2answers
393 views

Loops to create nested loops

Is there a way to use a loop to create more nested loops? E.g. Doing this for (int i = 0; i < iterations; i++) { //Do stuff for (int ii = 0; ii < ...
0
votes
1answer
105 views

Recursion, iteration, and …? [closed]

Here are three common code structures that apply a function multiple times: foo(x) { if basecase(x) return k else return foo(g(x)) } uses recursion. for i in 0..10 { n *= bar(i) } uses ...
0
votes
0answers
108 views

Does loop unrolling on a JIT platfrom (.NET or JVM) provide any benefit

I know in C, you can use loop unrolling (unwinding) to help reduce branching in your code but at the expense of program size. That seems to work when you compile to a target machine, however, does it ...
2
votes
1answer
131 views

Break big method into 2 methods, first containing a “for” loop and second a “break”

A method grew too big for its own good, and I need to break it up into two separate methods. def big_method(dct): # Initial code # ... for i in dct: # More code # ... ...
2
votes
2answers
216 views

How to iterate between these elements

I have an array of elements: int[] elem = new int[] {A, B, C}; I need to calculate the sum of ALL the combinations of those elements, where only some of the elements can be optionally selected. I ...
-2
votes
1answer
114 views

How to name variables without plural in a for-each loop? [closed]

How do you name loop variables when the list item is named after something without a plural? For instance (in python): [x for x in sheep]. x is not a great name, but sheep have/has no plural that ...
8
votes
7answers
1k 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, ...
0
votes
1answer
160 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 ...
1
vote
1answer
499 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
236 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
41 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 ...
1
vote
1answer
176 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
68 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
1k 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
108 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
287 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
5k 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
2k 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
96 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
767 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
155 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
79 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
643 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
324 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
1k 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
488 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 ...
41
votes
2answers
5k 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
106 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
123 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
323 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 ...
101
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
2k 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
277 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
30k 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
18k 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
385 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 ...