Add 'subsequences' and 'permutations' to Data.List (ticket #1990), discussion period end

[Twan van Laarhoven]

Twan van Laarhoven wrote:
> Hello all,
> 
> As Thomas Hartman noted in a recent cafe thread [1], haskell 1.3 
> included the functions 'subsequences' and 'permutations'. I think these 
> functions are quite useful, and I don't know why they were ever removed. 
> This is a proposal to add these two functions to Data.List. The 
> implementation is taken directly from the Haskell 1.3 report [2].
> 
> Trac ticket: #1990
> Discussion period ends: January 7th (since there is a holiday comming up)

The discussion period for this proposal is over. Everyone here seems to 
agree it is a good idea.

The patch attached to the trac ticket contains the best versions discussed 
in this thread:
  - Wolfram(kahl at cas.mcmaster.ca)'s version of subsequences
  - my permutations8c

Can someone with the power to do so apply this patch?

Twan