[Haskell-cafe] a regressive view of support for imperative programming in Haskell

Paul Hudak paul.hudak at yale.edu
Wed Aug 8 14:20:39 EDT 2007

All of the recent talk of support for imperative programming in Haskell 
makes me really nervous.  To be honest, I've always been a bit 
uncomfortable even with monad syntax.  Instead of:

do x <- cmd1
     y <- cmd2
     return e

I was always perfectly happy with:

cmd1 >>= \x->
cmd2 >>= \y->
return e

Functions are in my comfort zone; syntax that hides them takes me out of 
my comfort zone.

In my opinion one of the key principles in the design of Haskell has 
been the insistence on purity.  It is arguably what led the Haskell 
designers to "discover" the monadic solution to IO, and is more
generally what inspired many researchers to "discover" purely functional 
solutions to many seemingly imperative problems.  With references and 
mutable data structures and IO and who-knows-what-else to support the 
Imperative Way, this discovery process becomes stunted.

Well, you could argue, monad syntax is what really made Haskell become 
more accepted by the masses, and you may be right (although perhaps 
Simon's extraordinary performance at OSCOM is more of what we need).  On 
the other hand, if we give imperative programmers the tools to do all 
the things they are used to doing in C++, then we will be depriving them 
of the joys of programming in the Functional Way.  How many times have 
we seen responses to newbie posts along the lines of, "That's how you'd 
do it in C++, but in Haskell here's a better way...".

I hope I don't start a flame war with this post -- I'm just expressing 
my opinion, which admittedly is probably regressive rather than 
progressive :-).


Professor Paul Hudak
Department of Computer Science    Office: (203) 432-1235
Yale University                   FAX:    (203) 432-0593
P.O. Box 208285                   email:  paul.hudak at yale.edu
New Haven, CT 06520-8285          WWW:    www.cs.yale.edu/~hudak

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