A gem from the past (Goto)

[Lars Fosdal 1791]

Fun observations on the GoTo topic: https://jerf.org/iri/post/2024/goto/

[Sherlock 663]

Nice find @Lars Fosdal

[Anders Melander 1782]

1 hour ago, Lars Fosdal said:

Fun observations on the GoTo topic: https://jerf.org/iri/post/2024/goto/

Quote

When I see modern code that uses goto, I actually find that to be a marker that it was probably written by highly skilled programmers.

True, but don't say that out loud.

sEE, i'M uSiNg GoToS; iM A hiGhLy SkIlLeD pRoGraMmEr!

 

[Pat Foley 51]

Here is a dangerous example of Goto causing endless loop you never finish this gamebook's first edition.

In the gamebook You Can Be The Stainless Steel Rat by Harrison. There's an example of a typo goto 290 should be goto 190.

 

https://stainlesssteelrat.fandom.com/wiki/You_Can_Be_The_Stainless_Steel_Rat 

 

[Brandon Staggs 277]

Quote

 DELETE FROM shibboleths WHERE value LIKE "%goto%". Dumping on modern goto is not smart and wise and a sign of a good programmer, it’s a sign you don’t understand why goto is… or rather, was… bad.

That's great!

[A.M. Hoornweg 144]

On 11/4/2022 at 7:08 PM, dummzeuch said:

I actually used a goto for debugging today. The reason was that at the end of a function I check the result and for a particular result I want to repeat the code in the function in order to step through it:

function whatever: SomeType;
label
  RepeatMe;
begin
RepeatMe:
  // some code that generates the result
  if Result = ResultIWantToDebug then
    goto RepeatMe; // <== put a breakpoint here
  // some more code
 end;

 

 

No need for this, the debugger has that functionality built-in:

 

-Set a breakpoint on your corner case condition and wait until it fires

-Right-click the line where you want to "go to"

-Enter submenu "Debug"

-Select menu item "Set next statement". The debugger will jump here when you single-step through your code.

 

 

 

[pmcgee 10]

Something I posted on the ADUG forum ... this C code (when I saw it) was posted on twitter as an amusing post about C.

 

[ Cursed C code ]

 

But after I'd thought about it for a bit, it occurred to me that maybe I could do the same in Delphi.

And we can. 🙂

 

{$APPTYPE CONSOLE}
program Project1;

type
  range_struct = record
      type
         Tstate = (at_start, in_loop, done);
      var
         stop, step,
            i, start : integer;
         state       : Tstate;

      function    resume()  : integer;    
      constructor λ ( _start, 
                      _stop : integer; 
                      _step : integer = 1);
  end;

  constructor range_struct.λ( _start, _stop, _step:integer);
  begin
      start := _start;
      stop  := _stop;
      step  := _step;
      state := at_start;
  end;

  function range_struct.resume() : integer;
  label α,β,δ;
  begin
           case state of
                at_start : goto α;
                in_loop  : goto β;
                done     : goto δ;
           end;

     α :   i:=start;
           repeat
               begin
                   state := in_loop;
                   exit(i);
     β :           i     := i + step;
               end
           until i >= stop;
           state := done;
     δ :   exit(0);
  end;

begin
   var ρ := range_struct.λ(1,20,2);
   var π := range_struct.λ(2,20,2);

   for var i in [1..5] do begin
       writeln('a   ',i:2, 'th call : ', ρ.resume);
       writeln('  b ',i:2, 'th call : ', π.resume);
   end;

   writeln;
   writeln('Mwah ha ha. GOTO is back, baby!');
   readln;
end.

That wasn't the original function-calling code that I had posted.
It was only after a bit of mental digestion that I realised that this is (in my opinion) a really good, simplified, understandable model of a coroutine.

 

... and soon after I found out the original C code was part of an article commenting on c++ coroutines : https://probablydance.com/2021/10/31/c-coroutines-do-not-spark-joy/

 

Edited April 24 by pmcgee

[Die Holländer 45]

In the early BASIC times, like for the ❤️ ZX-Spectrum ❤️ there were

no functions or procedures but instead they introducted a way to

jump to another part of the source and return to the next line after

the jump. The statements: Gosub and Return.

 

10 LET A=0
20 PRINT "ENTER A NUMBER: "
30 INPUT N
40 GOSUB 100
50 PRINT "THE RESULT IS ";A
60 END

100 A = N * 2
110 RETURN

[Sherlock 663]

That reminds me:

Quote

BASIC programmers never die, they GOSUB and never RETURN.

 

[Cristian Peța 103]

On 4/25/2024 at 9:38 AM, Die Holländer said:

In the early BASIC times, like for the ❤️ ZX-Spectrum ❤️ there were

no functions or procedures but instead they introducted a way to

jump to another part of the source and return to the next line after

the jump. The statements: Gosub and Return. 

ZX-Spectrum BASIC was like an easier assembler where you use CALL and RET (Z80 assembler).

[Bill Meyer 337]

There is a classic, if dusty, article from Donald Knuth:
https://pic.plover.com/knuth-GOTO.pdf

[David Heffernan 2345]

On 4/26/2024 at 12:04 PM, Cristian Peța said:

ZX-Spectrum BASIC was like an easier assembler where you use CALL and RET (Z80 assembler).

Speccie basic was a terrible language. The beeb had a much better variant. 

[Die Holländer 45]

On 4/28/2024 at 8:17 AM, David Heffernan said:

Speccie basic was a terrible language. The beeb had a much better variant. 

Ahh, a typical reaction that started in that time..

 

My Commodore 64 is much better.

My Apple is much better than your Windows

My Iphone is much better than you Android phone.

My Javascript language is much better than ...

[David Heffernan 2345]

1 hour ago, Die Holländer said:

Ahh, a typical reaction that started in that time..

 

My Commodore 64 is much better.

My Apple is much better than your Windows

My Iphone is much better than you Android phone.

My Javascript language is much better than ...

Well, the Speccie and the 64 did have better games. The 64 had epic sound. The beeb was more used for hobbyist coding then the other computers of that age. And the beeb did have by far the best programming language of these. There were real differences. 

[Lars Fosdal 1791]

I still have a Memotech MTX512 in storage 🙂

 

[Leif Uneus 43]

Ahh, the horror of programming games with the Commodore VIC-20 using the tape recorder ...