3 ms·

When Dijkstra wrote that quote in 1975 he didn't had Visual Basic in mind, he was thinking the much older BASIC dialects that used line numbers and GOTOs for fl

When Dijkstra wrote that quote in 1975 he didn't had Visual Basic in mind, he was thinking the much older BASIC dialects that used line numbers and GOTOs for flow control. Dijkstra was trying to promote structured programming languages like Algol and Visual Basic is based on the QBasic dialect which has full structured programming features like WHILE and FOR loops, IF that would work with compound statements (that is have the THEN part be more than a single command), local variables, functions, recursion, etc. It might be hard to image nowadays but there was a time when those weren't available to all languages. Though note that the next year after Dijkstra wrote that quote, the original Dartmouth BASIC actually got structured features. Though it wouldn't be until QBasic that you'd see a (popular) BASIC dialect having those in home computers. Regardless, this quote was outdated long before Visual Basic 1 was made, let alone VB6.

zozbot234 7y ago
GOTO for flow control is not that bad, it's just a tail call after all. The real damage is things like having everything be global variables. But part of that was a technical limitation, as things like "proper" call stacks and reentrant code as the default still had plenty of overhead, and even FORTRAN didn't support them.
- badsectoracula 7y ago
  I'm not sure what you have in mind but in the 1975 dialects of BASIC the code was something like 10 REM Grab input 20 GOSUB 1000 30 IF VALUE=BAR THEN GOTO 100 40 IF VALUE=BAZ THEN GOTO 200 50 IF VALUE=BLA THEN GOTO 300 60 GOTO 20 100 REM Bar stuff 110 blahblah 199 RESUME 200 REM Baz stuff 210 blahblah 299 RESUME 300 REM Bla stuff 310 blahblah 399 RESUME 1000 REM Code that grabs input 1010 blahblah 1100 RESUME Or just here is some actual BASIC game: https://github.com/peteri/ClassicBasic/blob/master/Games/king.bas https://github.com/peteri/ClassicBasic/blob/master/Games/kin... Note that this is a bit more readable than what people worked with since now you have syntax highlighting. I'm not sure where tail calls enter in the picture... there wasn't even support for functions, at best you had GOSUB/RESUME which was essentially assembly-like CALL/RET.
  - zozbot234 7y ago
    > I'm not sure where tail calls enter in the picture... GOTO essentially involves setting the continuation of your program to something other than the following instruction(s). That's what a tail call does. No "functions" involved except as a high-level description.
  - stOneskull 7y ago
    did they use resume before return.. i had no idea. i loved how going from c64 basic to amiga basic, you didn't need line numbers anymore
  - laumars 7y ago
    I don't think that example you've posted is right (the grab input one, not the game on Github). Firstly, RESUME was to continue execution after an error (eg ON ERROR RESUME NEXT). I think RETURN is what you might have meant? Secondly, you cannot RESUME/RETURN from a GOTO. I think you meant GOSUB; which was a crude approximation of subroutines. BASIC did also have GOTO as well though.
    - badsectoracula 7y ago
      Yes you are right, i meant GOSUB/RETURN. Though instead of "RESUME" (which should have been RETURN) most programs would use GOTO 20 (in an opposite expression of what Dijkstra wrote about, i accidentally used a 'function call' idiom instead of a spaghetti 'jump wherever' one :-P).
  - int_19h 7y ago
    In a world where you "call" functions with GOSUB, GOTO is an equivalent of a tail call.
- hermitdev 7y ago
  Goto has its place. It's not evil, but should be used judiciously. After all, C family constructs such as break, continue are glorified/specialized, albeit scoped and unlabelled gotos. One of the places I like gotos is when I need to break out of a nested loop. A goto to outside of the outer loop is far more obvious than a flag and a conditional to break from the parent nested loop. It also generates better machine code and uses fewer registers, at least in debug mode. Sure, goto can be abused, just like every other language construct. They have their time and place, though.
  - mrighele 7y ago
    The issue was not the presence of goto itself, but the fact that is was one of the main tools for flow control, while as you say it should be used sparingly. It is like having an army of soldiers armed with a David Crockett[1] instead of a regular rifle. Things may get ugly fast. [1] https://en.m.wikipedia.org/wiki/Davy_Crockett_(nuclear_device) https://en.m.wikipedia.org/wiki/Davy_Crockett_(nuclear_devic...

zozbot234 7y ago

GOTO for flow control is not that bad, it's just a tail call after all. The real damage is things like having everything be global variables. But part of that was a technical limitation, as things like "proper" call stacks and reentrant code as the default still had plenty of overhead, and even FORTRAN didn't support them.

badsectoracula 7y ago
I'm not sure what you have in mind but in the 1975 dialects of BASIC the code was something like 10 REM Grab input 20 GOSUB 1000 30 IF VALUE=BAR THEN GOTO 100 40 IF VALUE=BAZ THEN GOTO 200 50 IF VALUE=BLA THEN GOTO 300 60 GOTO 20 100 REM Bar stuff 110 blahblah 199 RESUME 200 REM Baz stuff 210 blahblah 299 RESUME 300 REM Bla stuff 310 blahblah 399 RESUME 1000 REM Code that grabs input 1010 blahblah 1100 RESUME Or just here is some actual BASIC game: https://github.com/peteri/ClassicBasic/blob/master/Games/king.bas https://github.com/peteri/ClassicBasic/blob/master/Games/kin... Note that this is a bit more readable than what people worked with since now you have syntax highlighting. I'm not sure where tail calls enter in the picture... there wasn't even support for functions, at best you had GOSUB/RESUME which was essentially assembly-like CALL/RET.
- zozbot234 7y ago
  > I'm not sure where tail calls enter in the picture... GOTO essentially involves setting the continuation of your program to something other than the following instruction(s). That's what a tail call does. No "functions" involved except as a high-level description.
- stOneskull 7y ago
  did they use resume before return.. i had no idea. i loved how going from c64 basic to amiga basic, you didn't need line numbers anymore
- laumars 7y ago
  I don't think that example you've posted is right (the grab input one, not the game on Github). Firstly, RESUME was to continue execution after an error (eg ON ERROR RESUME NEXT). I think RETURN is what you might have meant? Secondly, you cannot RESUME/RETURN from a GOTO. I think you meant GOSUB; which was a crude approximation of subroutines. BASIC did also have GOTO as well though.
  - badsectoracula 7y ago
    Yes you are right, i meant GOSUB/RETURN. Though instead of "RESUME" (which should have been RETURN) most programs would use GOTO 20 (in an opposite expression of what Dijkstra wrote about, i accidentally used a 'function call' idiom instead of a spaghetti 'jump wherever' one :-P).
- int_19h 7y ago
  In a world where you "call" functions with GOSUB, GOTO is an equivalent of a tail call.
hermitdev 7y ago
Goto has its place. It's not evil, but should be used judiciously. After all, C family constructs such as break, continue are glorified/specialized, albeit scoped and unlabelled gotos. One of the places I like gotos is when I need to break out of a nested loop. A goto to outside of the outer loop is far more obvious than a flag and a conditional to break from the parent nested loop. It also generates better machine code and uses fewer registers, at least in debug mode. Sure, goto can be abused, just like every other language construct. They have their time and place, though.
- mrighele 7y ago
  The issue was not the presence of goto itself, but the fact that is was one of the main tools for flow control, while as you say it should be used sparingly. It is like having an army of soldiers armed with a David Crockett[1] instead of a regular rifle. Things may get ugly fast. [1] https://en.m.wikipedia.org/wiki/Davy_Crockett_(nuclear_device) https://en.m.wikipedia.org/wiki/Davy_Crockett_(nuclear_devic...