Term.Positions

Positions and replacement in terms.

Documentation

type Position = [Int]

A position in a term is a list of integers.

atPos :: Ord a => Term a -> Position -> Term a

t atPos p returns the subterm of term t at position p. The standard notation for t atPos p is t|_p. atPos accounts for AC symbols by interpreting n-ary operator applications *[t1,t2,..tk-1,tk] as binary applications t1*(t2*..(tk-1*tk)..).

replacePos :: Ord a => Term a -> (Term a, Position) -> Term a

t replacePos (s,p) returns the term t' where the subterm at position p is replaced by s. The standard notation for t replacePos (s,p) is t[s]_p. replacePos accounts for AC symbols in the same ways as atPos. FIXME: The AC can be optimized.

positionsNonVar :: (Show a, Show b) => VTerm a b -> [Position]

positionsNonVar t returns all the non-variable positions in the term t. positionsNonVar accounts for AC symbols in the same ways as atPos.