4 ms·

I've always wondered why goto is actually considered harmful. I really should read the original paper by Djikstra...

by chris_wot 7y ago

saagarjha 7y ago
It encourages spaghetti code.
- Someone1234 7y ago
  Not using it can also create spaghetti code. For example the "alternatives" often suggesting for exiting a multi-tiered loop (which often add additional boilerplate, additional variables, etc that all need to be maintained/bug free).
  - FartyMcFarter 7y ago
    Indeed. Despite not having actual goto, Java went out of their way to have labeled loops and the "break label_name" syntax in order to avoid this awkwardness.
- jjuhl 7y ago
  [RAII](https://en.cppreference.com/w/cpp/language/raii https://en.cppreference.com/w/cpp/language/raii) to the rescue..
GrumpyYoungMan 7y ago
Read David Tribble's "Go To Statement Considered Harmful: A Retrospective" instead: http://david.tribble.com/text/goto.html http://david.tribble.com/text/goto.html . It contains the entire text of Dijkstra's paper and goes over its meaning in a modern context on a paragraph-by-paragraph basis. It's very well written and makes clear the "encourages spaghetti code" argument, while true at the time, applied in a era where basic control flow constructs that we now take for granted did not exist in commonly used languages.
- nybble41 7y ago
  Thank you for the recommendation; that was a very interesting read. I find that I can't quite agree with the last "nontrivial goto" example, though. This version without explicit gotos is actually shorter, and IMHO not really any more difficult to follow: int parse(void) { Token tok; while ((tok = gettoken()) != END) { while (!shift(tok)) if (!reduce(tok)) return ERROR; } return ACCEPT; } I will say that any language without goto, or where the use of goto is discouraged, should at least provide guaranteed tail-call elimination as an alternative. In this case the gotos could easily be converted into loops, but not every algorithm is so accommodating.
gbacon 7y ago
See also Structured programming with go to statements[0] by Donald E. Knuth. [0]: https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.103.6084 https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.103...

I've always wondered why goto is actually considered harmful. I really should read the original paper by Djikstra...

saagarjha 7y ago

It encourages spaghetti code.

Someone1234 7y ago
Not using it can also create spaghetti code. For example the "alternatives" often suggesting for exiting a multi-tiered loop (which often add additional boilerplate, additional variables, etc that all need to be maintained/bug free).
- FartyMcFarter 7y ago
  Indeed. Despite not having actual goto, Java went out of their way to have labeled loops and the "break label_name" syntax in order to avoid this awkwardness.
jjuhl 7y ago
[RAII](https://en.cppreference.com/w/cpp/language/raii https://en.cppreference.com/w/cpp/language/raii) to the rescue..

GrumpyYoungMan 7y ago

Read David Tribble's "Go To Statement Considered Harmful: A Retrospective" instead: http://david.tribble.com/text/goto.html http://david.tribble.com/text/goto.html . It contains the entire text of Dijkstra's paper and goes over its meaning in a modern context on a paragraph-by-paragraph basis. It's very well written and makes clear the "encourages spaghetti code" argument, while true at the time, applied in a era where basic control flow constructs that we now take for granted did not exist in commonly used languages.

nybble41 7y ago
Thank you for the recommendation; that was a very interesting read. I find that I can't quite agree with the last "nontrivial goto" example, though. This version without explicit gotos is actually shorter, and IMHO not really any more difficult to follow: int parse(void) { Token tok; while ((tok = gettoken()) != END) { while (!shift(tok)) if (!reduce(tok)) return ERROR; } return ACCEPT; } I will say that any language without goto, or where the use of goto is discouraged, should at least provide guaranteed tail-call elimination as an alternative. In this case the gotos could easily be converted into loops, but not every algorithm is so accommodating.

gbacon 7y ago

See also Structured programming with go to statements[0] by Donald E. Knuth. [0]: https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.103.6084 https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.103...