7mo ago

[History] An editor letter by Edsger Dijkstra, titled: "go to statements considered harmful" (march 1968).

dl.acm.org Letters to the editor: go to statement considered harmful | Communications of the ACM

In this letter, Dijkstra talks about readability and maintainability in a time where those topics were rarely talked about (1968). This letter was one of the main causes why modern programmers don't have to trouble themselves with goto statements. Older languages like Java and C# still have a (discouraged) goto statement, because they (mindlessly) copied it from C, which (mindlessly) copied it from Assembly, but more modern languages like Swift and Kotlin don't even have a goto statement anymore.

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TIL that C# and Java have a goto statement.
- Forget about goto, the latest version of C# introduced what's essentially comefrom.
  
  Please don't link to medium articles. That page is terrible to visit.
  
  Looks fine on Firefox on Android with uBlock Origin. 🤷‍♂️
  
  I'm running exactly the same and it doesn't look fine on my end.
  
  Huh. Maybe it's NoScript, then.
  
  Could be. I'm getting forced to make an account and such. That's why I hate medium.
  
  To be fair, await is a bit more like comefrom, and it's been around for a few releases now.
  
  async/await was introduced in version 4.5, released 2012. More than a few releases at this point!
  
  How is await like comefrom, any more than threading is like comefrom? The variable context is preserved and you have no control over what is executed before the await returns.
  
  What...? That is a terrible idea.
  
  It's scary as fuck, yeah, but, to be fair, it's only intended to be used by code generators, and it's quite awkward to use outside of them.
- Java doesn't. Well, it's a reserved keyword but it's not implemented.
  
  Yeah but we got labels with continue and break, so we can pseudo goto.
  
  Following that logic if, else and while are also "pseudo goto" statements.
  There's nothing wrong with conditional jumps - we couldn't program without them. The problem with goto specifically is that you can goto "anywhere".
  
  If pretty much gets compiled to a goto statement. Well more a jumpif but same principle
- In C# at least, goto can take you between case labels in a switch statement (rather than using fallthrough), which I don't view as being nearly as bad. For example, you can do goto case 1 or goto default to jump to another case.
  The only other use of goto I find remotely tolerable is when paired with a labelled loop statement (like putting a label right before a for loop), but honestly Rust handles that far better with labelled loops (and labelled block expressions).
  
  I've programmed C# for nearly 15 years, and have used goto twice . Once to simplify an early break from a nested loop, essentially a nested continue. The second was to refactor a giant switch statement in a parser, essentially removing convoluted while loops, and just did a goto the start.
  It's one of those things that almost should never be used, but the times it's been needed, it removed a lot of silliness.

58 comments