[Template-haskell] Re: [Haskell] Proposal: Allow "\=" for field update in record update syntax

[S. Alexander Jacobson]

Since operators can't start with a ':', is there an in-principle 
reason TH does not support : operators?  The syntax below would be 
really nice to have.



On Fri, 18 Feb 2005, Sander Evers wrote:

>
>> Then we could have e.g. (:=) and (:\=) and end up with a
>> syntax that looks like this:
>>
>>    rec // field :\= fn . field2 := val
>>
>> And that is BETTER than the Haskell syntax that I originally proposed.
>
> This syntax is also nice for composition of update functions, which is useful
> with nested records:
>
> data Country = Country {capital :: City, ...}
> data City = City {inhabitants :: Int, ...}
>
> birth_in_capital :: Country -> Country
> birth_in_capital = capital :\= (inhabitants :\= (+1))
>
> This also shows that it would be useful to make :\= associate to the right.
>

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S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com