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

learn more… | top users | synonyms

99
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 ...
50
votes
6answers
10k views

Who created the idea(s) of the first loop constructs?

while (1) { if (1+1==2) { print "Yes, you paid attention in Preschool!"; } else { print "Wait... I thought 1+1=2"; } } As a developer, we all have to use ...
46
votes
7answers
6k views

Why are semicolons and commas interchanged in for loops?

In many languages (a wide list, from C to JavaScript): commas , separate arguments (e.g. func(a, b, c)), while semicolons ; separate sequential instructions (e.g. instruction1; instruction2; ...
39
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 ...
18
votes
4answers
17k 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 ...
10
votes
7answers
4k views

C# foreach improvements?

I run into this often during programming where I want to have a loop count index inside of a foreach and have to create an integer, use it, increment, etc. Wouldn't it be a good idea if there was a ...
9
votes
2answers
2k views

How to unit test method that returns a collection while avoiding logic in the test

I am test-driving a method that is to generate a collection of data objects. I want to verify that the properties of the objects are being set correctly. Some of the properties will be set to the same ...
8
votes
5answers
2k 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 ...
8
votes
7answers
692 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, ...
7
votes
5answers
473 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 = ...
7
votes
3answers
7k views

Does it make a difference if I declare variables inside or outside a loop in Java? [duplicate]

Possible Duplicate: Where do you declare variables? The top of a method or when you need them? Does it make a difference if I declare variables inside or outside a loop in Java? Is this ...
7
votes
1answer
512 views

Loop fusion example using aspect-oriented framework

I had recently read a paper 'Aspect-Oriented Programming' by Gregor Kiczales and others, and found there the loop fusion example. Here is a definition of the loop fusion from the paper …the loop ...
6
votes
3answers
650 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 ...
6
votes
4answers
2k 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: // ...
5
votes
2answers
446 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 ...
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 ...
4
votes
5answers
611 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 ...
4
votes
2answers
408 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
2k views

Decrementing/Incrementing loop variable inside for loop. Is this code smell?

I have to read lines from a text file in sequential order. The file is a custom text format that contains sections. If some sections are out of order, I would like to look for the starting of the next ...
4
votes
2answers
245 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 ...
4
votes
2answers
2k views

Loop Invariants in Python

I have a bit of experience with loop invariants but I'm not really clear on them. I'm trying to learn them through an example in Python. Can someone point one out or help me understand? I've ...
4
votes
1answer
393 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) { ...
4
votes
3answers
280 views

Is there an idiom for a loop that executes some block of instructions between iterations? (In Ruby in particular)

I often need to do some operations in a loop and some other operations between the iterations. A simple example would be collecting words from an array into a string, spelled backwards and separated ...
4
votes
1answer
413 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 ...
3
votes
3answers
692 views

Is there a way to add unique items to an array without doing a ton of comparisons?

Please bare with me, I want this to be as language agnostic as possible becuase of the languages I am working with (One of which is a language called PowerOn). However, most languanges support for ...
3
votes
2answers
404 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, ...
3
votes
5answers
2k views

Declaring functions in order to avoid explicit nested loops

My programming professor has told me that it is a good programming practice (at least in C/C++) to declare a function with the inner loop when nesting loops (not for loops, since when, i.e. looping ...
3
votes
5answers
226 views

Term for Performance Issues Due to Looping [closed]

Is there a term for performance issues caused by someone creates a loop that performs hundreds or thousands of actions that could have been done in bulk? My example is that I keep running into loops ...
3
votes
2answers
75 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 ...
3
votes
1answer
899 views

Loop invariant vs Assertions

I have an exam on Programming Concepts this Saturday and I am struggling to find some information to understand some concepts better. What is the difference between loop invariant and assertion? To ...
3
votes
4answers
266 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 ...
3
votes
2answers
1k views

Repetitive Drawing in Javascript & Canvas

Creating an HTML5 page using canvas and javascript to draw a set number of musical staves on the page, spaced a pre-determined amount in between. What I have is re-drawn on top of the canvas 10 ...
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 ...
2
votes
3answers
218 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
3answers
13k 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.
2
votes
1answer
91 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
203 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
2answers
263 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 ...
2
votes
1answer
39 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 ...
2
votes
1answer
101 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 && ...
2
votes
0answers
65 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 ...
1
vote
2answers
1k 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 ... ...
1
vote
1answer
287 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 ...
1
vote
3answers
343 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
2answers
77 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 ...
1
vote
3answers
143 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; } ...
1
vote
1answer
217 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 ...
1
vote
2answers
663 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 ...
1
vote
1answer
213 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 ...
1
vote
3answers
88 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 ...