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#!/usr/bin/python3
from collections import namedtuple
from .lexer import lexer, operators
# Stores a token's type and value, and optionally the position of the first
# character in the lexed stream.
class Token(namedtuple('Token', ['type', 'val', 'pos'])):
__slots__ = ()
# Custom constructor to support default parameters.
def __new__(cls, type, val='', pos=None):
return super(Token, cls).__new__(cls, type, val, pos)
def __str__(self):
return self.val
# Ignore position when comparing tokens. There is probably a cleaner way of
# doing these.
__eq__ = lambda x, y: x[0] == y[0] and x[1] == y[1]
__ne__ = lambda x, y: x[0] != y[0] or x[1] != y[1]
__lt__ = lambda x, y: tuple.__lt__(x[0:2], y[0:2])
__le__ = lambda x, y: tuple.__le__(x[0:2], y[0:2])
__ge__ = lambda x, y: tuple.__ge__(x[0:2], y[0:2])
__gt__ = lambda x, y: tuple.__gt__(x[0:2], y[0:2])
# Only hash token's value (we don't care about position, and types are
# determined by values).
def __hash__(self):
return hash(self[1])
# Return a list of tokens in [text].
def tokenize(text):
lexer.input(text)
return [Token(t.type, t.value, t.lexpos) for t in lexer]
# Return a one-line string representation of [tokens].
def stringify(tokens):
def token_str(t):
if t.type in ('PERIOD', 'COMMA'):
return str(t) + ' '
if t.type in operators.values():
return ' ' + str(t) + ' '
return str(t)
return ''.join(map(token_str, tokens))
# Yield the sequence of rules in [code].
def split(code):
tokens = tokenize(code)
start = 0
for idx, token in enumerate(tokens):
if token.type == 'PERIOD' and idx - start > 1:
yield stringify(tokens[start:idx])
start = idx + 1
# Return a list of lines in [code] and a list of rule ranges.
def decompose(code):
lines = []
rules = []
rule_start = 0 # lowest line number in the current rule
line = [] # tokens in the current line
break_line = True # for each comma, go to a new line
parens = [] # stack of currently open parens/brackets/braces
for t in tokenize(code) + [Token('EOF')]:
# Always break the line on a semicolon, even inside parens.
if t.type == 'SEMI':
if line:
lines.append(tuple(line))
line = []
lines.append((t,))
continue
# Break the line on these tokens if we are not inside parens. Don't
# append the final token unless it is the :- operator.
if break_line and t.type in ('PERIOD', 'FROM', 'COMMA', 'EOF'):
# Only append :- at the end of the line, ignore commas and periods.
if t.type == 'FROM':
line.append(t)
# Append nonempty lines to the output list.
if line:
lines.append(tuple(line))
line = []
# Commit a new rule if it contains some lines.
if t.type in ('PERIOD', 'EOF') and rule_start < len(lines):
rules.append((rule_start, len(lines)))
rule_start = len(lines)
continue
# Handle parens.
if t.type == 'LPAREN':
# Disallow breaking lines inside "name( )" (e.g. member(X, L)) but
# not other ( ).
if line and line[-1].type == 'NAME':
parens.append('paren')
break_line = False
else:
parens.append('ignore')
elif t.type in ('LBRACKET', 'LBRACE'):
# Disallow breaking lines inside "[ ]" and "{ }".
parens.append('paren')
break_line = False
elif parens:
if t.type in ('RPAREN', 'RBRACE', 'RBRACKET'):
parens.pop()
break_line = 'paren' not in parens
# Append this token to the current line.
line.append(t)
return lines, rules
# Format a list of [lines] according to [rules] (as returned by decompose).
def compose(lines, rules):
code = ''
for start, end in rules:
for i in range(start, end):
line = lines[i]
if i > start:
code += ' '
code += stringify(line)
if i == end-1:
code += '.\n'
elif i == start:
code += '\n'
else:
if line and line[-1].type != 'SEMI' and lines[i+1][-1].type != 'SEMI':
code += ','
code += '\n'
return code.strip()
# Rename variables in [tokens] to A0, A1, A2,… in order of appearance.
def rename_vars(tokens, names=None):
if names is None:
names = {}
next_id = len(names)
# Return a new list.
tokens = list(tokens)
for i in range(len(tokens)):
if tokens[i].type == 'PERIOD':
names.clear()
next_id = 0
elif tokens[i] == Token('VARIABLE', '_'):
tokens[i] = Token('VARIABLE', 'A{}'.format(next_id))
next_id += 1
elif tokens[i].type == 'VARIABLE':
cur_name = tokens[i].val
if cur_name not in names:
names[cur_name] = 'A{}'.format(next_id)
next_id += 1
tokens[i] = Token('VARIABLE', names[cur_name])
return tokens
# Helper function to remove trailing punctuation from lines and rename
# variables to A1,A2,A3,… (potentially using [var_names]). Return a tuple.
def normalized(line, var_names=None):
# Remove trailing punctuation.
i = len(line)
while i > 0:
if line[i-1].type not in ('COMMA', 'PERIOD', 'SEMI'):
break
i -= 1
return tuple(rename_vars(line[:i], var_names))
# transformation = before → after; applied on line which is part of rule
# return mapping from formal vars in before+after to actual vars in rule
# line and rule should of course not be normalized
def map_vars(before, after, line, rule):
mapping = {}
new_index = 0
for i in range(len(before)):
if line[i].type == 'VARIABLE':
formal_name = before[i].val
if line[i].val != '_':
actual_name = line[i].val
else:
actual_name = 'New'+str(new_index)
new_index += 1
mapping[formal_name] = actual_name
remaining_formal = [t.val for t in after if t.type == 'VARIABLE' and t.val not in mapping.keys()]
remaining_actual = [t.val for t in rule if t.type == 'VARIABLE' and t.val != '_' and t.val not in mapping.values()]
while len(remaining_actual) < len(remaining_formal):
remaining_actual.append('New'+str(new_index))
new_index += 1
for i, formal_name in enumerate(remaining_formal):
mapping[formal_name] = remaining_actual[i]
return mapping
# Basic sanity check.
if __name__ == '__main__':
code = 'dup([H|T], [H1|T1]) :- dup(T1, T2). '
lines, rules = decompose(code)
print(compose(lines, rules))
var_names = {}
before = rename_vars(tokenize("dup([A0|A1], [A2|A3])"), var_names)
after = rename_vars(tokenize("dup([A0|A1], [A5, A4|A3])"), var_names)
line = lines[0]
rule = tokenize(code)
mapping = map_vars(before, after, line, rule)
print(mapping)
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