Here's an old friend...GOTO
lazarus / 8-Other

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minesadorada · 2014-07-30 19:03

There is still a use for GOTO, surely? 

I read somewhere that the fpc compiler loves GOTO statements, as they
optimise to machine code easily.

It's surprising that the current version of Laz/FPC still supports the
LABEL and GOTO commands because they have been unfashionable for
decades.  I did remember the syntax though..

Quick 'n dirty string input routine using LABEL and GOTO that won't
let go until szPW is assigned a non-blank string:
Code: [Select]var
  iRetries:Integer;
  sz,szPw:String;
LABEL STARTAGAIN,RETRYPW;
begin
iRetries:=3;
RETRYPW:
sz:='';
If iRetries=0 then GOTO STARTAGAIN;
  If InputQuery(
  Format('Input password.  Tries left %d',[iRetries]),
  'Please type in a non-blank passowrd',TRUE, sz) then
  szPW:=sz
  else // user closed query
   begin
    Dec(iRetries);
    GOTO RETRYPW;
   end;

  STARTAGAIN: // user cancelled 3 times
  iRetries:=3;
  If (sz = '') then GOTO RETRYPW; // user entered nothing
ShowMessage(szPW);

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marcov · 2014-07-30 19:16

goto is mostly used in lowlevel code. Remember that Free Pascal
implements its own RTL in itself. Having goto eliminates some uses for
assembler.

Also, jumping with goto out multiple nested IFs is usually still
faster than without. (afaik both FPC and Delphi have this trait)

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BeniBela · 2014-07-30 20:13

I think you must add COMEFROM to the syntax, too.

That can be really nice to write

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minesadorada · 2014-07-30 21:06

Quote from: BeniBela on July 30, 2014, 10:13:44 pmI think you must add
COMEFROM to the syntax, too.

That can be really nice to write
Oh I like that.

If there was a statement DidntMeanToGOTO or OOPS it could replace
EXCEPT, and be more truthful...

Try
 ...code..
OOPS
..apology here
End;

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Edson · 2014-07-31 02:51

Quote from: minesadorada on July 30, 2014, 11:06:35 pmQuote from:
BeniBela on July 30, 2014, 10:13:44 pmI think you must add COMEFROM to
the syntax, too.

That can be really nice to write
Oh I like that.

If there was a statement DidntMeanToGOTO or OOPS it could replace
EXCEPT, and be more truthful...

Try
 ...code..
OOPS
..apology here
End;

Casually, I was looking for new instructions for a language that I'm
writing. I will include these .

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skalogryz · 2014-07-31 03:14

Quote from: Edson on July 31, 2014, 04:51:18 amCasually, I was looking
for new instructions for a language that I'm writing. I will include
these .
Lolcode?

@minesadorada, you've made a perfect example of how, where and why NOT
to use goto.