From: Andreas Launila <ruby-talk@...>
Date: 2007-06-07T23:10:58+09:00
Subject: Re: Gecode/R - Request for syntax feedback

James Edward Gray II wrote:
> On Jun 6, 2007, at 5:21 AM, Andreas Launila wrote:
> 
>> James Edward Gray II wrote:
>>> On Jun 5, 2007, at 2:43 PM, Andreas Launila wrote:
>>>
>>>> == Issues ==
>>>>
>>>> === Describing (linear) constraints ===
>>>
>>>> A problem with the above is that people might look at it and
>>>> instinctively think that it's something that does not have a side
>>>> effect. Therefore prepending some sort of method might convey that
>>>> intention better. For instance we could allow people to write the
>>>> following.
>>>>
>>>> constrain x + y == z
>>>
>>> RSpec works a lot like this.  It has you define expectations with syntax
>>> like:
>>>
>>>   some_obj.should     equal(whatever)
>>>   some_obj.should_not equal(whatever)
>>>
>>>> Fitting words other than "constrain" might be "assert", "post" and
>>>> "add".
>>>
>>> I like the word "constrain."  If you go the RSpec route though, you will
>>> probably also want a negative form and I don't know what that would be.
>>>
>>
>> That would be a nice solution. The best word I can think of for
>> "constrain" is "constrain_negation", which is probably far from perfect.
>>
>> constrain_negation x + y == z
> 
> Yuck.  And I mean that in the nicest possible way.  ;)
> 
>> Another variation would be to use a combination of constrain and RSpec's
>> should/should_not.
>>
>> constrain (x + y).must == z
>> constrain (x + y).must_not == z
> 
> That's not too bad.  I think my biggest complaint there is that it makes
> the flow of the line a little hard to follow.  Perhaps must/must_not
> could replace constrain altogether though:
> 
> must     x + y == z
> must_not x + y == z
> 
> That doesn't read too well though, does it?
> 

I think that must/must_not would make a fairly interesting syntax in the
sense that it reads very well. Therefore I have tried some examples at
http://gecoder.lokorin.org/dev/wiki/Syntax_test#must.2Fmust_not .

They probably require skipping "constrain" though and replacing it with
something block-like, it just doesn't read right otherwise.

-- 
Andreas Launila