Jump to content

Talk:Control flow

Page contents not supported in other languages.
From Wikipedia, the free encyclopedia
Former good article nomineeControl flow was a good articles nominee, but did not meet the good article criteria at the time. There may be suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
Article milestones
June 16, 2006Good article nomineeNot listed

Unnecessary verbiage?[edit]

First paragraph has " an imperative or a declarative program ". Can the words imperative and declarative be omitted since we're not actually singling out one kind of program? (talk) 14:02, 23 October 2014 (UTC)[reply]

Can control flow be used for declarative?[edit]

Declarative programming definition in Wikipedia says: "In computer science, declarative programming is a programming paradigm, a style of building the structure and elements of computer programs, that expresses the logic of a computation without describing its control flow.". However in this article we see that control flow can be described for declarative as well. This is confusing. — Preceding unsigned comment added by (talk) 07:56, 8 April 2015 (UTC)[reply]


From Murray Langton:

Nobody commented on my outline for a complete rewrite, so I have done the rewrite.

"Constructs to be avoided"[edit]

Wikipedia is not prescriptive; it can at best report what others prescribe. "You should not [otherwise] [do X]" is something Wikipedia must never, ever say. "Smith and Thompson and Jones all agree you shouldn't [do X]" and "nobody [does X] anymore [because]" are fine.

The part about goto was redundant with the section on goto, so I deleted it. The historical and arcane control flow structures were not discussed, so I merged them in their appropriate sections. I'm sad to say the link to Knuth's paper was broken and I couldn't find a substitute; hope you paid those ACM subscription fees. 21:26, 14 September 2005 (UTC)[reply]

Redirect from Elif[edit]

There is a redirect from the ELIF wikipedia entry, but although this is a subclass of the IF command, there is no reference to ELIF in this article

fixed --Krischik T 13:12, 24 February 2006 (UTC)[reply]

Control flow constructs are a special kind of statements[edit]

IMHO Statements are a larger group containing control flow constructs as special case. For example: Many programming languages have assignment-, declaration-, I/O- and assert-statements which are not control flow constructs. I improved the statement article a little bit and added some links to it.

Lanugage examples.[edit]

I think the modlue has to many language examples. We should realy concentrate on the actual contruct and how it works and leave programming language dependent part to pages describing that language - or even and better Wikibooks.

As it is I think the page is not clear enough

--Krischik T 11:49, 17 February 2006 (UTC)[reply]

I think it's biased towards procedural languages (e.g. Pascal, C), which aren't too different. We should add examples from languages with more unconventional syntaxen and semantics — Preceding unsigned comment added by (talk) 17:44, 23 June 2012 (UTC)[reply]

Loop with test in the middle[edit]

As Ada actualy got the Loop with test in the middle I wonder ot it actually is a Proposed control structure. --Krischik T 07:25, 23 February 2006 (UTC)[reply]

How does Ada cope when you want to exit from the middle of several nested loops (as per example of searching 2-D array)? Murray Langton 21:40, 23 February 2006 (UTC)[reply]
Sorry, query about wrong control structure. Murray Langton 21:42, 23 February 2006 (UTC)[reply]
You can name a look and then use exit Outer_Loop when Condition; --Krischik T 07:03, 24 February 2006 (UTC)[reply]

Exceptions vs continuations[edit]

In 6 Structured non-local control flow it says: "Exceptions, conditions, and continuations are three common sorts of non-local control constructs."

Are PL/1 conditions any different from exceptions? If so, the article should explain how; if not, the two sections should be combined.

-- Brock

Interesting point. The difference is a bit like if then goto vs. if then else One is structured the other is not but apart from that they do the same thing. BTW: Some Basic dialects and Rexx have that contruct as well. --Krischik T 13:08, 24 February 2006 (UTC)[reply]
and C has for(;;) or while(1). similar thing happens (talk) 18:03, 9 March 2008 (UTC)[reply]

I don't know about PL/1, but the distinguishing feature of conditions in Common Lisp is that they can be ignored (if they are not errors) and resumed (with restarts). In other words, unlike exceptions, the stack is not always necessarily unwound. --FOo (talk) 23:44, 9 March 2008 (UTC)[reply]

GA failed[edit]

For these reasons:

  1. Lead fails to represent the article.
  2. The example that follow this, In many programming languages, a label is an identifier. should state which language it is from.
  3. For every piece of code the language should be mentioned beside it.
  4. For a fuller discussion on the drawbacks of goto, see Goto., should go in the front.
  5. Inline external links should be placed in a footnotes or references section at the bottom of the article.
  6. A number of authors have pointed out that using goto is often acceptable, like whom for example or where is this piece of info from?
  7. Subroutines can be made much more useful by providing them with parameters and what are the disadvantages of not providing params?
  8. In need of wikilinks for definition of words, e. g., tree-traversals, overhead, stack ...
  9. The program will end execution after the third line without continuing into the function. ... why?
  10. The fact that such minimalism is possible does not necessarily mean that it is desirable and who said that? ref please or make it more NPOV.
  11. after all, computers theoretically only need one machine instruction (subtract one number from another and branch if the result is negative), but practical computers have dozens or even hundreds of machine instructions., simplistic view maybe ref this part too. Is this really necessary in an encyclopedia.
  12. Languages whose final keyword is of the form: end + initial keyword (with or without space in the middle) tend to be easier to learn and read. says who?
  13. The Choice section should demonstrate statements universally without needing the Ada language. Thus turn every code into Ada-free code or wikilink to other wikipedia articles like: If should point to Conditional statement.
  14. The tables should conform to the Footnotes method for the comments added to them.
  15. The Anecdotal evidence section needs more introduction for non-experts. Lincher 02:29, 16 June 2006 (UTC)[reply]
(Changed User:Lincher's above list from bullets to numbered list to facilitate discussion - Dmeranda 18:17, 30 June 2006 (UTC))[reply]
For (1), I rewrote the lead section so it should meet WP guidelines -- Dmeranda 18:22, 30 June 2006 (UTC)[reply]

Early exit and infinite loops[edit]

Deep break/early exit is simulated in C and C++ not through exceptions but via goto's and labels. Also, infinite loops which are conditionless are simulated through labels and gotos as well; this avoids a conditional check if you really want an infinite loop.


Python for-else and while-else constructs[edit]

There was some confusion over when the else-clause of a Python for or while loop is executed. A simple test case shows this

for i in [42]:
    if i == 42:
        print 'Breaking out of for loop'
    print 'In else clause of for loop'

when run outputs only "Breaking out of for loop". Likewise changing "i == 42" to "i == 99" and re-running only outputs "In else clause of for loop". So the else clause is executed on if the loop is not exited early by a break statement. -- Dmeranda 16:37, 19 March 2007 (UTC)[reply]

Redirected from "then"[edit]

If you type in the word: "then" it comes to this page, however this is about Control Flow. LostNecromancer 22:58, 10 April 2007 (UTC)[reply]

The redirect is probably due to the keyword "then" as used in the "if-then" statement, which one of the most common control flow statements in many programming languages. It should probably more approriately redirect to Conditional statement though as that article is more specific than this one; and unless somebody thinks there is an even more common use of the word "then" which has an article in WP. Remember, redirects are cheap and the main problem with them is when they may point to an obscure article while a better target exists. See Wikipedia:Redirect. - Dmeranda 20:24, 11 April 2007 (UTC)[reply]
I've changed the redirects for Then and Else to now point to the Conditional statement article instead of this one. - Dmeranda 20:47, 11 April 2007 (UTC)[reply]

Merge proposal[edit]

This article (Control flow) is quite long - even, I would argue, overlong - and the section called "Choice" is now long enough to be an article in its own right. However, there is already an article about conditional statements, which does not include all the material in this section. If there is to be a separate article about conditional statements, that article should be longer and more in-depth than the corresponding section on this page. Therefore, I propose merging the material in the "Choice" section into conditional statement, and leaving behind a Main Article link, possibly with a short summary (it's usual to have such a summary).

Some might argue that case statements are not conditional statements. However, they are frequently classified as such, and they meet the general definition given in the conditional statement article, so I don't think this position would be justified.—greenrd 13:33, 14 April 2007 (UTC)[reply]

I support this merge as the section while informative is a bit redundant outside of the main artice, they should be merged and a short summary left on the control flow page with a main article link Adam McCormick 14:39, 14 April of the term, nor even any mention of anything which it is easy to connect lexically. Please correct. Donal Fellows (talk) 15:34, 29 December 2008 (UTC)[reply]

usage of "Continuation"[edit]

The "Loop system cross reference table" has a "continuation" column, but from what I can tell, it's not the normal meaning of continuation in computer science; for instance, I'm reasonably sure Java doesn't support continuations, but it's listed as having them in the column. Is "escape continuation" meant instead, or what? --Cybercobra (talk) 03:32, 18 February 2009 (UTC)[reply]

Presumably what is meant is the continue keyword as per C etc, ie exit early form this iteration and start the next one.1Z (talk) 00:02, 17 July 2011 (UTC)[reply]


It seems anomalous that conditionals and switches have their own articles, but there is a huge wodge of material on loops here. 1Z (talk) 00:08, 17 July 2011 (UTC)co[reply]

C and C++ have an infinite loop[edit]

for(;;); executes forever. — Preceding unsigned comment added by (talk) 13:01, 26 March 2012 (UTC)[reply]

That's true, but what's your point? There's lots of possible infinite loops. Dmcq (talk) 13:17, 26 March 2012 (UTC)[reply]

Section on "Categories"[edit]

The section on categories says that loop is "the same as conditional branch". But that is not true. What is introduced with loops is the concept of iteration, and there is no way to express iteration just by using sequences of conditionals. — Preceding unsigned comment added by 2003:88:6907:9216:E854:9D05:CA8D:611E (talk) 12:26, 10 February 2017 (UTC)[reply]

External links modified[edit]

Hello fellow Wikipedians,

I have just modified one external link on Control flow. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

  • If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
  • If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 17:16, 12 August 2017 (UTC)[reply]

There is no such thing as "control flow". The correct term is "flow control".[edit]

WEEkped1 (talk) 01:30, 21 December 2018 (UTC)On the contrary...They have 2 separate meanings. One is "flow control" ;is a computer task. Works by correct and discernable directions imbedded in code in 2D. CONSTRAINED TO MOVE GENTLY, LIKE A WATERFALL. It's own known or unknown parenting. The other is the manipulation of the computer limits by formulae and square box repetition. The "control flow" is a constant path smooth and concise that moves according to other paths and instructions. It can be changed. A new part of code that increases knowledge to the computer. It can be altered. It can be expelled, force(s) increased or decreased, jammed, under scrutiny of inspection. It can lock out or open. It is flexible when correctly coded. It can hold files, thus open to directions flowing as "control flow" is used constantly. Both "control flow" and "flow control" are wide amplitudes fitting in the Cos/Sin of a moving map. Technology will require more from dx/diag. Then the width and depth, color(s). Moving parts and characters and trees. They are manipulated by point and click. So the coder does the "flow control" AND THE COMPUTER ALLOWS FOR MOVEMENT programmed by extensive outer forces known in short: magic. It is done behind and in front of the hardware--WEEkped1 (talk) 01:30, 21 December 2018 (UTC) Or... "Control Flow" term considered meaningless (because it's wrong)[reply]

In the (correct and meaningful) terms "flow control" and "control of flow", the word flow is an abbreviation of "flow of execution". In addition, the word flow means something similar to "sequence". So the term "flow of execution" means, roughly, the "sequence in which instructions are executed".

And this is what is controlled. That is, it is flow that is controlled. It is NOT control that is flowed!

Just as we have "temperature control" (or the "control of temperature"), and "volume control" (or the "control of volume"), and "motion control" (or the "control of motion"), so too do we have "flow [of execution] control" (or the "control of flow [of execution]").

I can only speculate about how such an abomination as the meaningless term "Control flow" came to be used so frequently. Perhaps somewhere, decades ago, people sat in CS lecture theatres struggling to keep up with their lecturers and by mistake scribbled down the words "control flow" in their notes 10 seconds after the lecturer had used the correct term, "flow control". (Or perhaps the lecturers made the mistake.) And failing to properly parse and understand the components of the term, and probably as a result of much buggy parroting, the meaningless term "control flow" gradually became used with increasing frequency, spreading like a disease. :)

Think about it: control statements (selection statements like if and switch, loop statements like while and do, jump statements like break, continue etc) control what happens next. They control the sequence. The flow. They control along which path of the FLOW diagram execution will proceed. They don't "flow" (as though "flow" means something like decide or control!) which path of a "control diagram" execution proceeds along!

By all means, use the term "Control flow!" as an imperative, as a command (e.g., next time you're speaking to a voice-activated valve??). But "control flow" has NO MEANING as a thing, as a compound noun. Control is not an adjective to describe a type of flow!

Therefore I propose that this whole article be renamed "Flow Control" - the correct term - and that every reference within the Wikipedia universe to "control flow" (ughh!) be suitably modified too.

-- Andrew Fallows (andyfallows at btinternet.com) (talk) 14:14, 17 October 2017 (UTC)[reply]

I note that htere are already two articles entitled <Flow control (subject)>. Murray Langton (talk) 06:08, 21 December 2018 (UTC)[reply]
Article title seems fine. "control" is used adjunctively. And the term is fixed by popular language use, not our editors. Web searching "control flow" finds almost only article topic. Web searching "flow control" finds much about flow of data, water, air, cement, foods, beverages, pharmaceuticals, and so on. A computer may control flow of data of indefinite types. But the term "control flow" is delightfully more specific about which flow, the flow of a (control intrinsic) instruction pointer through data. Noun adjunct grammar lets people say "chicken soup" to clearly specify soup of chicken, and likewise lets "control flow" refer to flow of control. Samuel Erau (talk) 14:15, 14 March 2024 (UTC)[reply]
Correction: What flows is not the instruction pointer itself, but where it points to. Samuel Erau (talk) 14:30, 14 March 2024 (UTC)[reply]
I vaguely recalled the term as "flow control" from my study of computer science in high school and college, but it turns out on Google Books that as early as 1984 there was a workshop on "control flow" hosted by Friedrich L. Bauer, Edsger W. Dijkstra, and C.A.R. Hoare. I've never heard of Bauer, but Dijkstra and Hoare, of course, are legends in the computer science community. The official Java Language Specification by James Gosling also uses the term "control flow". So the current article title is the correct one. --Coolcaesar (talk) 10:48, 25 March 2024 (UTC)[reply]