+
−from types import UnicodeType
+
−
+
−def gqn(val):
+
−    """
+
−    The geographic quote name function; used for quoting tables and 
+
−    geometries (they use single rather than the double quotes of the
+
−    backend quotename function).
+
−    """
+
−    if isinstance(val, basestring):
+
−        if isinstance(val, UnicodeType): val = val.encode('ascii')
+
−        return "'%s'" % val
+
−    else:
+
−        return str(val)
+
−
+
−class SpatialOperation(object):
+
−    """
+
−    Base class for generating spatial SQL.
+
−    """
+
−    def __init__(self, function='', operator='', result='', beg_subst='', end_subst=''):
+
−        self.function = function
+
−        self.operator = operator
+
−        self.result = result
+
−        self.beg_subst = beg_subst
+
−        try:
+
−            # Try and put the operator and result into to the
+
−            # end substitution.
+
−            self.end_subst = end_subst % (operator, result)
+
−        except TypeError:
+
−            self.end_subst = end_subst
+
−
+
−    @property
+
−    def sql_subst(self):
+
−        return ''.join([self.beg_subst, self.end_subst])
+
−
+
−    def as_sql(self, geo_col):
+
−        return self.sql_subst % self.params(geo_col)
+
−
+
−    def params(self, geo_col):
+
−        return (geo_col, self.operator)
+
−
+
−class SpatialFunction(SpatialOperation):
+
−    """
+
−    Base class for generating spatial SQL related to a function.
+
−    """
+
−    def __init__(self, func, beg_subst='%s(%s, %%s', end_subst=')', result='', operator=''):
+
−        # Getting the function prefix.
+
−        kwargs = {'function' : func, 'operator' : operator, 'result' : result,
+
−                  'beg_subst' : beg_subst, 'end_subst' : end_subst,}
+
−        super(SpatialFunction, self).__init__(**kwargs)
+
−
+
−    def params(self, geo_col):
+
−        return (self.function, geo_col)