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Date: Mon, 9 Feb 2015 15:05:22 +0400
Message-ID: <CA+9eiLur0DVGBNkzFkiTj3POL5B9H0D8=5wE-wuwN2O-FQZNyg@mail.gmail.com>
To: Joe Watkins <pthreads@pthreads.org>
Cc: Yasuo Ohgaki <yohgaki@ohgaki.net>, Stanislav Malyshev <smalyshev@gmail.com>, 
	PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e015386101e70c9050ea5bf50
Subject: Re: [PHP-DEV] Design by Contract
From: dmitry@zend.com (Dmitry Stogov)

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invariant is for classes only. It should be called before and/or after each
method to check object consistency.

syntax with expressions may work if we put constraints before the function
body .

function foo($a int): int
    require(expr1)
    require(expr2, msg)
    return(expr3)
{
}

Yasuo, I would suggest to describe both syntax options.

Thanks. Dmitry.

On Mon, Feb 9, 2015 at 1:46 PM, Joe Watkins <pthreads@pthreads.org> wrote:

> Morning Yasuo,
>
>     Can you explain what invariant is for ?
>
>     I prefer a list of contracts with a single expression, over blocks of
> expressions in one contract.
>     An IDE can just as easy generate a block of code or set of contracts,
> so it's really just a matter of how complex it makes the implementation if
> you allow any block of code in the contract. I think it does make it
> unnecessarily complicated to implement, I can be wrong.
>
>    If there is going to be two rfc's, I will vote no on the annotations
> based one, I'd rather no time was wasted on even writing it; Before you
> convince anyone that DBC is a good idea you have to convince them
> annotations is a good idea, many have tried and failed.
>
> Cheers
> Joe
>
> On Mon, Feb 9, 2015 at 10:34 AM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:
>
>> Hi Dmitry and Joe,
>>
>> On Mon, Feb 9, 2015 at 6:01 PM, Dmitry Stogov <dmitry@zend.com> wrote:
>>
>>> Usage of "return" is a good idea.
>>> The more heads the better result :)
>>>
>>
>> Less additional reserved word :)
>> So I'll use "require" and "return" for D like RFC.
>> We haven't talk much about invariants. I'll write my idea.
>>
>> Current RFC is large enough already, I'll prepare new one.
>> We may decide what to do with 2 RFCs.
>>
>> We have choices for with block or without block. I prefer with block
>> version, since
>> assert expression could be messy. With block, IDE may do it's jobs. i.e.
>> Hide blocks.
>>
>> ==============================================
>> Function/Method
>>
>> [With block]
>> function foo()
>> require {
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>> }
>> return {
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>> }
>> invariant {
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>> }
>> {
>>    // body
>> }
>>
>> _OR_
>>
>> [Without block]
>> function foo() {
>>   require(assert-expr, 'msg');
>>   require(assert-expr, 'msg');
>>   require(assert-expr, 'msg');
>>   invariant(assert-expr, 'msg');
>>   invariant(assert-expr, 'msg');
>>   invariant(assert-expr, 'msg');
>>   return(assert-expr, 'msg');
>>   return(assert-expr, 'msg');
>>   return(assert-expr, 'msg');
>>
>>   // function body
>> }
>>
>>
>> Currently, following code wouldn't work (PHP 7.0.0-dev)
>> ----------
>> assert(function() {return FALSE;}, 'AAAAA');
>> ----------
>>
>> For block version, which do you prefer, allow any PHP syntax or assert
>> only?
>> People may use anonymous function  to do fancy jobs anyway if it's
>> supported.
>>
>> No block version only accepts EXPR obviously, but anonymous function may
>> be used with this as well.
>>
>>
>> ==============================================
>> Class invariants
>>
>> [With block]
>> class Foo {
>>   __invariants() {
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   }
>> }
>>
>> _OR_
>>
>> [Without block]
>> class Foo {
>>   __construct() {
>>     invariant(assert-expr, 'msg'); // Only allow in __construct()?
>> Allowing invariant.
>>     invariant(assert-expr, 'msg');
>>     invariant(assert-expr, 'msg');
>>   }
>> }
>>
>>
>> ==============================================
>> Global invariant
>>
>> I'm not sure if we should have
>>
>> function __invariants() {
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>> }
>>
>> _OR_
>>
>> invariant {
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>>   assert(assert-expr, 'msg');
>> }
>>
>> to assert global vars, whole app state, etc. It may be useful for unit
>> tests as well as app development.
>>
>>
>> I'll start working after I get comment from you.
>>
>> Regards,
>>
>> --
>> Yasuo Ohgaki
>> yohgaki@ohgaki.net
>>
>
>

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