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Developer Argues For 'Forgotten Code Constructs' Like GOTO and Eval (techbeacon.com)

Posted by EditorDavid on from the infinitely-abusable dept.

mikeatTB quotes TechBeacon: Some things in the programming world are so easy to misuse that most people prefer to never use them at all. These are the programming equivalent of a flamethrower... [But] creative use of features such as goto, multiple inheritance, eval, and recursion may be just the right solution for experienced developers when used in the right situation. Is it time to resurrect these four forgotten code constructs?
The article notes that the Linux kernel uses goto statements, and links to Linus Torvalds' defense of them. ("Any if-statement is a goto. As are all structured loops...") And it points out that eval statements are supported by JavaScript, Python, PHP, and Ruby. But when the article describes recursion as "more forgotten than forbidden," it begs the inevitable question. Are you using these "forgotten code constructs" -- and should you be?

11 of 600 comments (clear)

  1. Doing it wrong? by marc.pn.beaupre · · Score: 5, Insightful

    Honest question: Am I not supposed to use recursion? Am I missing something?

    1. Re:Doing it wrong? by j_kenpo · · Score: 5, Insightful

      I'm just as baffled by this. I wasn't aware that recursion went out of style. Just another tool in the algorithm and design pattern toolbox. Did I miss the memo that it was taboo as GOTO?

    2. Re:Doing it wrong? by religionofpeas · · Score: 4, Insightful

      2) It's possible to write any traversal algorithm using loops, without any recursion.

      Sure, but if that requires building your own stack, you haven't really gained anything.

    3. Re: Doing it wrong? by K.+S.+Kyosuke · · Score: 4, Insightful

      Every time you make a function call, some amount of bookkeeping data has to be stored on the stack

      Not necessarily, really, these days. But yes, if your compiler is really dumb, like in the 1970s, the difference can be significant.

      If you do "manual recursion", with a loop and a resizable container, then you can achieve lower overhead.

      Chances are that if you can do that easily, you should have done it in the first place, and if you can't, there was a reason for that.

      --
      Ezekiel 23:20
    4. Re: Doing it wrong? by religionofpeas · · Score: 4, Insightful

      So you consider it easier to change perfectly running code (for what reason?) instead of fixing the compiler settings?

      Sometimes, yes. The project was for a medical application, with 99% of the code written by others. I'm not going to change global compiler settings and risk exposing some optimization error, when I can simply change a few lines of my code.

    5. Re: Doing it wrong? by Anonymous Coward · · Score: 5, Insightful

      Well, most compilers convert most recursions into loops anyway: it is called tail recursion optimization.

      Correction: *some* compilers will convert *some specifically structured* tail-recursive function calls into loops.

      There are lots of ways to make recursive function calls not tail-calls which renders them ineligible for compiler optimization.

    6. Re: Doing it wrong? by david_thornley · · Score: 4, Insightful

      Some algorithms are naturally recursive. For example, in-order traversal of a binary tree is easiest described as: deal with the left child, deal with this node, deal with the right child. Tower of Hanoi is easily solvable with: Move all disks above the one you want to move to the other peg, move the disk you want to move to the peg you want to move to, move the disks you moved earlier to on top of the disk you wanted to move.

      In these cases, if you use loops, you're going to be making up all the stuff recursion is good for, and you're going to be maintaining your own stacks. There's no advantage to doing this rather than using recursion. If you were going to get into a loop and recurse indefinitely, if you translate it into loops you're going to get into a loop and push indefinitely.

      --
      "When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
    7. Re: Doing it wrong? by allo · · Score: 4, Insightful

      That's a termination condition: If you ever visit a node, which was visited before, stop.

      You do not follow the symlink 1000 times and then abort. You follow it one time and the next time you see a mark "followed it" and stop. Without error as successful termination of a directory traversal.

      You think such a link would be an invalid condition, but it is actually not. And it isn't even a special case to the algorithm, which has the invariant "always take a node, which wasn't visisted yet until there are no such nodes".

  2. I know what will happen one day. by LordHighExecutioner · · Score: 4, Insightful

    Somebody will publish a paper entitled: "Class statement considered harmful." and he will be applauded as the new IT guru!

    1. Re:I know what will happen one day. by cheesybagel · · Score: 4, Insightful

      IMO class inheritance is useless. Interfaces and properties are a good idea though.

  3. Re:Recursion is dead! by Anonymous Coward · · Score: 4, Insightful

    You should read "GOTO considered harmful" before you bash it.

    "Most programmers have heard the adage "Never use goto statements", but few of today's computer science students have the benefit of the historical context in which Dijkstra made his declaration against them. Modern programming dogma has embraced the myth that the goto statement is evil, but it is enlightening to read the original tract and realize that this dogmatic belief entirely misses the point."
    http://david.tribble.com/text/...

    In the bad old days, all you had was goto, and every program looked like spaghetti. Now that we have if...then...else, loops, switch-case statements,
    goto should only be used as a last resort (and every use should be justified). I've been a professional programmer for twenty years; last year I used goto *twice*.

    And never forget https://xkcd.com/292/