Meta-point: backward compatibility

apfelmus apfelmus at
Thu Apr 24 13:10:47 EDT 2008

Chris Smith wrote:
> I'm definitely not arguing for this ($) 
> associativity change, for example, and my objection is the backward 
> compatibility.  But ultimately, it's more like a combination of 
> incompatibility and the lack of a really compelling story on why it 
> should be one way or the other.  I have a hard time calling this a "fix"; 
> it's more like a change of personal taste.

The $ problem is an interesting one, for it has the following properties:

  1) Someone who learns Haskell for the first time will not complain
     about either associativity. Whether it's left or right associative
     is rather unimportant, it is how it is and either way is fine.

  2) But once the decision has been made, it's nigh impossible to change
     it, simply because everybody has relied on one particular
     associativity of $ all the time.

  3) Assuming that this associativity is a matter of taste, it only
     sounds fair to experiment and try different tastes. So, Cale has a
     Prelude with left associative $ and Lennart has a different personal
     Prelude as well and I'm going too taste a sip of either one and
     brew my own functional coffee. But in that situation, the defining
     property of a standard, namely that everybody uses the same $ , is
     gone, everybody would have to check which one is used in which

It's like being forced to eat chicken only because chicken lay eggs. 
Some may like it, some may not, but the eggs will hatch new chicken who 
lay new eggs for all eternity :)


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