Hello All,
I'm stumped by a problem that seems to me to be hard to
do efficiently in Haskell or any 'pure' functional language. That is,
making an inverse index.
The particular problem stems from a particularly efficient method of
string searching (at least it's efficient as an imperative algorithm)
which involves analysing the pattern string to find out the last
position in the pattern where each letter of the 'alphabet' appears and
make an array of such positions indexed on the letters of the alphabet.
I just cannot see an efficient way of writing this which doesn't create
more than one version of the array. It appears to need to update the
array for each occurrence of the letters.
Can anyone think of an efficient method. Monads?
