Re: If Statement with Declaration

[Jonathan Marler via Digitalmars-d]

On Wednesday, 19 July 2017 at 16:13:28 UTC, Swoorup Joshi wrote:
On Wednesday, 19 July 2017 at 15:31:08 UTC, ag0aep6g wrote:
On 07/19/2017 03:30 PM, sontung wrote:
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?

I'd prefer a new variant of `with`:

----
with (int i = someFunc()) if (i >= 0)
{
    // use i
}
----

It's slightly more verbose, but the meaning is clearer 
(arguable). It extends automatically to other control 
structures like `switch`.

I wouldn't have this new `with (declaration)` have the magic 
lookup rules of the existing `with (expression)`. It would be 
a simpler tool that I'd probably use more than the existing 
`with`.

I really prefer this over if. This just made sense, just at a 
glance

Could also make 'with' behave like 'if', where it could apply to 
a block or just a single statement, i.e.

// 'if' examples
if(x)
    doSomething

if(x)
{
    doSomething
}

// 'with' examples
with(auto x = 0)
    doSomething

with(auto x = 0)
{
    doSomething
}

This would automatically make it work with any statement:

with(auto x = 0) if(x)
{
   doSomething
}

with(auto x = 0) while(x)
{
   doSomething
}

Could also do multiple with statements

with(auto x = 0)
with(auto y = 0)
if(check(x, y))
{
    doSomething
}