context.py

from utils import Set
class Context:
    """A context is a set of symbols to the left, the symbol we're matching,
    and a set of symbols to the right. There may be more than one context per
    symbol, not all of which will be stored in one context."""
    def __init__(self,leftSymbols,middleSymbol,rightSymbols):
        assert(type(leftSymbols).__name__ == 'set')
        assert(type(rightSymbols).__name__ == 'set')
        self.leftSymbols=leftSymbols
        self.rightSymbols=rightSymbols
        self.middleSymbol=middleSymbol

    def __str__(self):
        return "#C<%s, %s, %s>" % (self.leftSymbols,self.middleSymbol,self.rightSymbols)

    def __repr__(self):
        return str(self)

    def __eq__(self,other):
        if self.leftSymbols != other.leftSymbols:
            return False
        if self.rightSymbols != other.rightSymbols:
            return False
        if self.middleSymbol != other.middleSymbol:
            return False
        return True

    def getLeftRegexes(self):
        """Returns a set of regexes that matches the right hand side of the expansion of the left symbols"""
        regexes = Set()
        for symbol in self.leftSymbols:
            regexes.update(symbol.getRightRegexes())
        return regexes

    def getMiddleRegexes(self):
        """Returns the set of regexes that matches the symbol we are coloring"""
        return self.middleSymbol.get_terminal_equivalent_regexes()

    def getRightRegexes(self):
        """Returns a set of regexes that matches the left hand side of the expansion of the right symbols"""
        regexes = Set()
        for symbol in self.rightSymbols:
            regexes.update(symbol.getLeftRegexes())
        return regexes