Query Parser

Main.hs

import Text.ParserCombinators.Parsec

data Query = And Query Query
           | Or Query Query
           | Not Query
           | Statement String deriving (Show)

andParser = do
    arg1 <- statementParser
    string " AND "
    arg2 <- statementParser
    return (And arg1 arg2)

orParser = do
    arg1 <- statementParser
    string " OR "
    arg2 <- statementParser
    return (Or arg1 arg2)

notParser = do
    char '-'
    negation <- statementParser
    return (Not negation)

subqueryParser = do
    char '('
    subquery <- queryParser
    char ')'
    return subquery

quotedStatementParser = do
    char '"'
    statement <- many (noneOf "\"")
    char '"'
    return (Statement statement)

singleStatementParser = do
    statement <- many (noneOf " ()")
    return (Statement statement)

statementParser = choice [
    try (notParser),
    try (subqueryParser),
    try (quotedStatementParser),
    singleStatementParser
    ]

queryParser = choice [
    try (andParser),
    try (orParser),
    statementParser
    ]

main = putStrLn $ show $ parse queryParser "(unknown)" "(-foo AND -\"bar plezant\") AND (-bar OR foo)"