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Subject: Re: [PHP-DEV] RFC Proposal: Maybe monad and execution time
 polymorphic methods
From: larry@garfieldtech.com (Larry Garfield)

On 3/21/16 10:23 PM, Côme Chilliet wrote:
> Le lundi 21 mars 2016, 17:04:30 Facundo Martinez Correa a écrit :
>> But then I realized the problem. There
>> are many times where we need uncertainty. Code is a reflection of reality,
>> and as such, it must reflect uncertainty. NULL is a good enough way to
>> express nonexistence, albeit a bad one. We have been using it in code for
>> years, but it is also used to say many things. Things that cause
>> uncertainty in the code. I receive a null, does it mean it doesn't exists?
>> That it will exist? Should I allow it? Is it a good value? I for sure don't
>> know. And in my experience, I have used it for many of those cases. And in
>> many situations that I'm not proud of, all of them at the same time.
> If your function is supposed to return a User and can’t, maybe it should throw an Exception.
> Just wanted to point out it can be a good alternative to returning NULL for error handling.
>
> Côme

In the PHP 7 and typing presentations I've been giving[1], I've 
advocated either:

1) Throw an exception if the rest of the code is going to break anyway.
2) Define an empty object with matching interface if you want an 
equivalent of 0/empty string.

While a monad sounds cool, it doesn't seem like the necessary language 
infrastructure is there for it at the moment.

[1] My most recent talk that has a section on returns:
https://youtu.be/rWDY4-LJils?t=2m38s (that's where the return type 
segment starts)
Slides:

https://www.palantir.net/presentations/midcamp2016-php7/

-- 
--Larry Garfield