[Haskell-cafe] Language extensions

[Andrew Coppin]

Tomasz Zielonka wrote:
> On Mon, May 28, 2007 at 11:43:47AM +0100, Andrew Coppin wrote:
>   
>> - Chapter 2 is... puzzling. Personally I've never seen the point of 
>> trying to check a program against a specification. If you find a 
>> mismatch then which thing is wrong - the program, or the spec?
>>     
>
> Knowing that one of them is wrong is already a very useful information,
> don't you think?
>   

My point is for most programs, trying to figure out exactly what you 
want the program to do is going to be much harder than implementing a 
program that does it.

Also, for most programs the spec is far more complicated (and hence 
prone to error) than the actual program, so...

>> - Chapter 12 is incomprehensible (to me at least). "Fun with Phantom 
>> Types" I've read it several times, and I still couldn't tell you what a 
>> phantom type is...
>>     
>
> Ironically, this chapter contains the following (at least the version
> at http://www.informatik.uni-bonn.de/~ralf/publications/With.pdf):
>
>      Of course, whenever you add a new feature to a language, you should
>      throw out an existing one (especially if the language at hand is
>      named after a logician). Now, for this chapter we abandon type
>      classes - judge for yourself how well we get along without
>      Haskell's most beloved feature.
>
> You've found a language extension soulmate! ;-)
>   

It amazes me that anybody would think removing type classes is a good 
idea... but there we are. :-}

> BTW, I really liked Ralf's chapter.
>   

It's a free country. ;-)

>> There are some bits that are sort-of interesting but not really to do
>> with anything I'm passionate about, and then there are bits that I
>> can't comprehend...
>>     
>
> Passionate... perhaps this is the root of the problem? Different people
> are passionate about different things.
>   

Well, more that some things make more sense to me than others. It's 
difficult to decide whether you're passionate about something or not if 
you can't understand what it is.