{-
CPG island grammar example, adapted from 'Biological Sequence Analysis' (Durbin et al)

Let us start by giving the grammar for CPG islands.
Also: Pretty comments ;-)
-}

{-
Grammar: CPG  -- the name of the grammar

N: P  -- islands 'Plus'
N: M  -- continents 'Minus'
N: S  -- start non-terminal

T: n  -- read a single nucleotide

S: S  -- symbol to start with

S -> start  <<< P     -- we could both in island,
S -> start  <<< M     -- or not island

P -> nil    <<<   e   -- no input left
P -> isl    <<< P n   -- stay on the island
P -> toisl  <<< M n   -- to island

M -> nil    <<<   e   -- no input left here
M -> cntnt  <<< M n   -- stay on the continent
M -> frmisl <<< P n   -- from island
//

-- Derive outside grammar, named GPC, from known source grammar.

-- Outside: GPC
-- Source: CPG
-- //

-- Emit both the inside and the outside grammar.

Emit: CPG
-- Emit: GPC
-}

Grammar: Two {i,j}
N: A{k = 3,l = 3}
N: B
S: A{k = 0}
A{k} -> ff <<< A{l}
A{k} -> ff <<< B
A{k} -> ff <<< A{k + 0}
//