The dreaded M-R

[Scott Turner]

Following the helpful call to attend to priorities, I reluctantly return to 
the M-R discussion. I believe a point has been missed that should be a part 
of this thread.

On 2006 January 30, Josef Svenningsson wrote:
> But the most important argument against M-R hasn't been put forward yet.
>
> Haskell is, and has always been, a non-strict language. *Not* a lazy
> language.

That is correct, but it is not a welcome argument. Haskell's unspecified 
evaluation order is elegant, and gives implementers a happy flexibility. But 
Haskell has no need to allow innovative experiments within the report.

On the contrary, practical Haskell programs and libraries rely on sharing. 
Without sharing, the humble Fibonacci example takes exponential time. If the 
report were to clearly mandate the sharing that nearly everyone counts on, it 
would be a benefit. The := syntax suggested by John Hughes is an obvious 
point at which sharing could be mandated. 

The wiki page 
http://hackage.haskell.org/trac/haskell-prime/wiki/MonomorphismRestriction
counts "introducing a concept of sharing into the report" as a negative. In 
the larger context of bolstering Haskell's support for mainstream 
applications, sharing is worthwhile.