-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/
-- | Generalization of parsec's expression parser.
--
-- Generalization of parsec's expression parser.
@package expression-parser
@version 0.1
module Text.ParserCombinators.Expression
-- | This data type specifies the associativity of operators: left, right
-- or none.
data Assoc
AssocNone :: Assoc
AssocLeft :: Assoc
AssocRight :: Assoc
-- | This data type specifies operators that work on values of type
-- a. An operator is either binary infix or unary prefix or
-- postfix. A binary operator has also an associated associativity.
data Operator p a
Infix :: (p (a -> a -> a)) -> Assoc -> Operator p a
Prefix :: (p (a -> a)) -> Operator p a
Postfix :: (p (a -> a)) -> Operator p a
-- | An OperatorTable is a list of Operator lists. The
-- list is ordered in descending precedence. All operators in one list
-- have the same precedence (but may have a different associativity).
type OperatorTable p a = [[Operator p a]]
-- | buildExpressionParser table term builds an expression parser
-- for terms term with operators from table, taking the
-- associativity and precedence specified in table into account.
-- Prefix and postfix operators of the same precedence can only occur
-- once (i.e. --2 is not allowed if - is prefix
-- negate). Prefix and postfix operators of the same precedence associate
-- to the left (i.e. if ++ is postfix increment, than
-- -2++ equals -1, not -3).
--
-- The buildExpressionParser takes care of all the complexity
-- involved in building expression parser. Here is an example of an
-- expression parser that handles prefix signs, postfix increment and
-- basic arithmetic.
--
--
-- expr = buildExpressionParser table term
-- <?> "expression"
--
-- term = parens expr
-- <|> natural
-- <?> "simple expression"
--
-- table = [ [prefix "-" negate, prefix "+" id ]
-- , [postfix "++" (+1)]
-- , [binary "*" (*) AssocLeft, binary "/" (div) AssocLeft ]
-- , [binary "+" (+) AssocLeft, binary "-" (-) AssocLeft ]
-- ]
--
-- binary name fun assoc = Infix (do{ reservedOp name; return fun }) assoc
-- prefix name fun = Prefix (do{ reservedOp name; return fun })
-- postfix name fun = Postfix (do{ reservedOp name; return fun })
--
buildExpressionParser :: (Monad p, Alternative p) => [[Operator p b]] -> p b -> p b