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Date: Wed, 15 Jul 2020 12:14:36 -0500
To: "php internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC][Discussion] Objects can be declared falsifiable
From: larry@garfieldtech.com ("Larry Garfield")

On Wed, Jul 15, 2020, at 11:59 AM, Marco Pivetta wrote:
> Hey Larry,
> <http://ocramius.github.com/>
> 
> 
> On Wed, Jul 15, 2020 at 6:55 PM Larry Garfield <larry@garfieldtech.com>
> wrote:
> 
> > I disagree entirely.  The value of a Maybe over just null is
> >
> > 1) You can bind to it even if the result is empty; the "if is null" check
> > gets abstracted away from the main code.
> >
> 
> That's correct: that's how the `Maybe` monad works too.

That... is what I'm describing?  A Maybe Monad?  

> > 2) You are forced to unwrap/extract the value if you're not just binding,
> > which makes it less likely you'll forget to check if it's null
> 
> 
> No need to unwrap: that's what `>>=` does for you.
> 
> Assuming you use psalm or phpstan, a program that doesn't use `>>=`, or
> forgets to check for `null` on `?T` does not type-check anyway, and can be
> rejected before even writing any runtime tests: that's sound.
> 
> Marco Pivetta

My Haskell experience is zilch, but since PHP lacks a dedicated bind operator that also magically unwraps, that doesn't seem relevant.  (Mind you, I'd be all for a dedicated bind operator that also auto-unwraps!  But that's not on the radar at the moment.)

--Larry Garfield