def OnceTD(operand, stop=None):
'''Performs a left to right depth first search/transformation that
stops as soon as the the transformation has been successfuly applied.
'''
if stop is None:
return iterate.Rec(lambda self: combine.Choice(operand, One(self)))
else:
return iterate.Rec(
lambda self: combine.Choice(operand, -stop * One(self)))
def AllTD(operand):
'''Apply a transformation to all subterms, but stops recursing
as soon as it finds a subterm to which the transformation succeeds.
'''
alltd = util.Proxy()
alltd.subject = combine.Choice(operand, All(alltd))
return alltd
def One(operand):
'''Applies a transformation to exactly one direct subterm of a term.'''
one = util.Proxy()
one.subject = congruent.Subterms(
# FIXME: write a non-recursive implementation
combine.Choice(congruent.Cons(operand, base.ident),
congruent.Cons(base.ident, one)),
base.fail)
return one
def DownUp(down=None, up=None, stop=None):
downup = util.Proxy()
downup.subject = All(downup)
if stop is not None:
downup.subject = combine.Choice(stop, downup.subject)
if up is not None:
downup.subject = combine.Composition(downup.subject, up)
if down is not None:
downup.subject = combine.Composition(down, downup.subject)
return downup
def Some(operand):
'''Applies a transformation to as many direct subterms of a term, but at list one.'''
some = util.Proxy()
some.subject = congruent.Subterms(
# FIXME: write a non-recursive implementation
combine.Choice(
congruent.Cons(operand, lists.Map(combine.Try(operand))),
congruent.Cons(base.ident, some),
),
base.fail)
return some
def Traverse(Subterms, down=None, up=None, stop=None, Enter=None, Leave=None):
'''Generic traversal.'''
traverse = util.Proxy()
traverse.subject = Subterms(traverse)
if Leave is not None:
traverse.subject = Leave(traverse.subject)
if stop is not None:
traverse.subject = combine.Choice(stop, traverse.subject)
if up is not None:
traverse.subject = combine.Composition(traverse.subject, up)
if down is not None:
traverse.subject = combine.Composition(down, traverse.subject)
if Enter is not None:
traverse.subject = Enter(traverse.subject)
return traverse
def AtSuffixR(operand):
atsuffix = util.Proxy()
atsuffix.subject = combine.Choice(congruent.Cons(base.ident, atsuffix),
operand)
return atsuffix
def AllBU(operand):
allbu = util.Proxy()
allbu.subject = combine.Choice(All(allbu), operand)
return allbu
def SomeBU(operand):
return iterate.Rec(lambda self: combine.Choice(Some(self), operand))
def SomeTD(operand):
return iterate.Rec(lambda self: combine.Choice(operand, Some(self)))
def OnceBU(operand):
return iterate.Rec(lambda self: combine.Choice(One(self), operand))
def __add__(self, other):
'''Addition operator. Shorthand for L{lib.combine.Choice}'''
#warnings.warn("using deprecated choice operator", DeprecationWarning, stacklevel=2)
from transf.lib import combine
return combine.Choice(self, other)
