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MarkShark

Thoughts on using begin end merely to limit inline var scope.

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I realize that this is going to be very subjective, but what are people's thoughts on using begin end just to limit the scope of an inline variable?  For example:

 

... code
begin
  var LocalString := 'My String';
  ... Use LocalString for something
end;
... more code  

Are there any caveats to doing so?   I know that doing this can cause an implicit try-finally for managed types, so I can see that being a performance factor in a loop and something to be aware of. It also seems like they've fixed the issues with the debugger and inline vars in Delphi 11 (at least in the simple cases I've tried), which makes them more usable.

 

-Mark

 

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program Project1;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils;

begin
  try
    { TODO -oUser -cConsole Main : Insert code here }
    var x:=5;
    inc(x, DayOfWeek(now));
    writeln(x);
    if x<5 then {break point here}
      writeln('x<5')
    else
      writeln('x>=5');

    readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

The debugger will say: 'Symbol was eliminated by linker'. In my opinion it's still not solved in debug configuration. I am still going to wait for fully implemented inline variables.

 

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In concept, it is great - but lack of support in the debugger is a problem.

If you have two blocks with var x := <whatever> it gets even more confused.

 

I love using inline vars for loops -> no use after the loop block and type inference saves you from having to declare the type.

 

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19 minutes ago, Lars Fosdal said:

no use after the loop block and type inference saves you from having to declare the type.

Saves you from declaring the type when it's working (eg. Currency).

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us C++ programmers have had this since the begining - it's very common to just use a pair { } and create a local variable that exists only for the extent of the braces

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IMHO using blocks just for this purpose only adds visual noise and needlessly increases LOCs

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11 hours ago, Fr0sT.Brutal said:

IMHO using blocks just for this purpose only adds visual noise and needlessly increases LOCs

When has an abundance of visual noise been a problem before with Pascal, the most verbose of languages!!! 

  • Haha 3

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Until the tooling catches up, I wouldn't recommend inline variables.  Refactoring can break, code formatting breaks, debugger gets confused...

 

I really jumped into inline var usage and quickly hit a wall.  Now they are banned from my code.

 

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2 hours ago, Darian Miller said:

Refactoring can break, code formatting breaks, debugger gets confused...

Sure, its only been what.. well under a decade 🙂

 

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We use inline vars quite a bit.  For loops, in particular - as well as for temporary variables.

But, yes, the tooling is lagging behind.

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10 hours ago, David Heffernan said:

When has an abundance of visual noise been a problem before with Pascal, the most verbose of languages!!! 

Looking at some " succinct " languages, I'd prefer verbosity...

Perl `sub deleteDoubleDots($) { while($_[0] = m/\.\./) { $_[0] = s/\/[^\/]*\/\.\.//; } }`

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9 minutes ago, Fr0sT.Brutal said:

Looking at some " succinct " languages, I'd prefer verbosity...

Perl `sub deleteDoubleDots($) { while($_[0] = m/\.\./) { $_[0] = s/\/[^\/]*\/\.\.//; } }`

Not wishing to defend Perl too much, but that function could be written more clearly with a named variable, but it would look much the same in any language. The regex wouldn't change. In fact the regex match and substitute syntax in Perl is actually very readable. I don't think the Delphi version would be clearer. 

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5 hours ago, Fr0sT.Brutal said:

Looking at some " succinct " languages, I'd prefer verbosity...

Perl `sub deleteDoubleDots($) { while($_[0] = m/\.\./) { $_[0] = s/\/[^\/]*\/\.\.//; } }`

There are worse:

Software History

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