Hi All,

Is minimal evaluation always enabled in D?

I want to write a function IsNull(), so that I can check the precondition as
follows:

  if (isNull(foo) ||
      isNull(foo.getBar) ||
      isNull(foo.getBar.getBar2)
  {
    return false;
  }
  // normal code goes here

If an argument is null, the IsNull() will return false. Internally it will be logged to console as well.

But I am not sure, if dmd-compiler generates code without minimal evaluation in some cases. If minimal evaluation is not always enabled. I cannot do precodition check in my way.

--Qian

> 
> if (isNull(foo) ||
>     isNull(foo.getBar) ||
>     isNull(foo.getBar.getBar2)
> {
>   return false;
> }

Update: If minimal evaluation is not always enabled, and foo.getBar is NULL. I will get a segfault when evaluating foo.getBar.getBar2.

On 06.04.2009 13:30, Qian Xu wrote:
> Hi All,
>
> Is minimal evaluation always enabled in D?
>
> I want to write a function IsNull(), so that I can check the precondition as
> follows:
>
>    if (isNull(foo) ||
>        isNull(foo.getBar) ||
>        isNull(foo.getBar.getBar2)
>    {
>      return false;
>    }
>    // normal code goes here
>
> If an argument is null, the IsNull() will return false. Internally it will
> be logged to console as well.
>
> But I am not sure, if dmd-compiler generates code without minimal evaluation
> in some cases. If minimal evaluation is not always enabled. I cannot do
> precodition check in my way.
>
> --Qian

If you mean short-circuit evalutation, I'm pretty sure that's always what the compiler does.

torhu wrote:

> 
> If you mean short-circuit evalutation, I'm pretty sure that's always what the compiler does.

Thanks. Somebody posted this link: http://digitalmars.com/d/1.0/expression.html#OrOrExpression