def combinator_reduce(lst, depth=MAX_DEPTH):
"""Reduce combinatory logic list of lists.
TODO: Incorporate other reduction strategies / evaluation orders.
"""
if not isinstance(lst, list): return lst
elif len(lst) == 0: return list()
elif depth < 0: raise CombinatorEvaluationDepthException
elif len(lst) > MAX_LENGTH: raise CombinatorEvaluationLengthException
else:
op, args = lst[0], lst[1:]
newdepth = depth-1
if isinstance(op, list):
return combinator_reduce( op + args, newdepth )
elif op == 'I' and len(args) >= 1:
return combinator_reduce( args[1:], newdepth)
elif op == 'K' and len(args) >= 2:
x,y,rest = args[0], args[1], args[2:]
return combinator_reduce( [x] + rest, newdepth)
elif op == 'S' and len(args) >= 3:
x,y,z,rest = args[0], args[1], args[2], args[3:]
return combinator_reduce( [x, z, [y, z]] + rest, newdepth )
else:
rest = map(lambda x: unlist_singleton(combinator_reduce(x, newdepth)), args)
if len(rest) == 0: return lst
else: return [op, ] + rest
def combinator_reduce(lst, depth=MAX_DEPTH):
"""
Reduce combinatory logic list of lists.
TODO: Incorporate other reduction strategies / evaluation orders.
"""
if not isinstance(lst, list): return lst
elif len(lst) == 0: return list()
elif (depth < 0): raise CombinatorEvaluationDepthException
elif (len(lst) > MAX_LENGTH): CombinatorEvaluationLengthException
else:
op, args = lst[0], lst[1:]
newdepth = depth-1
if isinstance(op, list):
return combinator_reduce( op + args, newdepth )
elif op == 'I' and len(args) >= 1:
return combinator_reduce( args[1:], newdepth)
elif op == 'K' and len(args) >= 2:
x,y,rest = args[0], args[1], args[2:]
return combinator_reduce( [x] + rest, newdepth)
elif op == 'S' and len(args) >= 3:
x,y,z,rest = args[0], args[1], args[2], args[3:]
return combinator_reduce( [x, z, [y, z]] + rest, newdepth )
else:
rest = map(lambda x: unlist_singleton(combinator_reduce(x, newdepth)), args)
if len(rest) == 0: return lst
else: return [op,]+rest
def parseScheme(s):
"""
Return a list of list of lists... for a string containing a simple lambda expression (no quoting, etc)
Keeps uppercase and lowercase letters exactly the same
e.g. parseScheme("(S (K (S I)) (S (K K) I) x y)") --> ['S', ['K', ['S', 'I']], ['S', ['K', 'K'], 'I'], 'x', 'y']
"""
x = sexp.parseString(s, parseAll=True)
return unlist_singleton( x.asList() ) # get back as a list rather than a pyparsing.ParseResults
def parseScheme(s):
"""
Return a list of list of lists... for a string containing a simple lambda expression (no quoting, etc)
Keeps uppercase and lowercase letters exactly the same
e.g. parseScheme("(S (K (S I)) (S (K K) I) x y)") --> ['S', ['K', ['S', 'I']], ['S', ['K', 'K'], 'I'], 'x', 'y']
"""
x = sexp.parseString(s, parseAll=True)
return unlist_singleton(
x.asList()) # get back as a list rather than a pyparsing.ParseResults