If Statement with Declaration

[Steven Schveighoffer via Digitalmars-d]

On 11/4/16 10:10 AM, Steven Schveighoffer wrote:
> On 11/3/16 6:29 PM, Jerry wrote:
>>
>> So I was thinking of a way of extending if statements that have
>> declarations. The following being as example of the current use of if
>> statements with declarations:
>>
>>     if(int* weDontPollute = someFunc())
>>     {
>>          // use weDontPollute
>>     }
>>
>> That's great and all, but it only works by checking if the variable
>> evaluates to true or false. Which is fine for a pointer but otherwise
>> useless for anything else, like integers where zero is usually valid
>> input (index for array). So currently the only way to do something like
>> this in the language, that i've found, is to use a for statement.
>>
>>     for(int i = someFunc(); i >= 0;)
>>     {
>>         // use i
>>
>>         break;
>>     }
>>
>> Not that ideal to use a for statement. It makes it hard to read and if
>> the break condition isn't there it might very well be an infinite loop.
>> So I was thinking of some sort of syntax like this:
>>
>>     if(int i = someFunc(); i >= 0)
>>     {
>>         // use i
>>     }
>> Thoughts on this sort of feature?
>
>
> Hm... what about something like:
>
> struct BoolCond(T, string cond)
> {
>    T val;
>    bool opCast(B)() if(is(B == bool))
>    {
>      return mixin("val " ~ cond);
>    }

Of course, I missed this:

      alias val this;

-Steve