Re: 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