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"""Simple code generator."""
from contextlib import contextmanager
from story3.grammar import Rule
HEADER = """\
# This is @generated code; do not edit!
from token import NAME, NUMBER, STRING, NEWLINE, ENDMARKER
from story3.memo import memoize
from story3.node import Node
from story3.parser import Parser
"""
class Generator:
def __init__(self, stream=None):
self.stream = stream # If None, write to sys.stdout.
self.indentation = ""
def put(self, *args):
# Note: print(..., file=None) prints to sys.stdout.
print(end=self.indentation, file=self.stream)
print(*args, file=self.stream)
@contextmanager
def indent(self):
save = self.indentation
try:
self.indentation += " "
yield
finally:
self.indentation = save
def gen_rule(self, rule):
self.put(f"@memoize")
self.put(f"def {rule.name}(self):")
with self.indent():
self.put(f"self.show_rule({rule.name!r}, {rule.alts!r})")
self.put(f"pos = self.mark()")
for i, alt in enumerate(rule.alts):
self.gen_alt(alt, rule, i)
self.put(f"self.show_index(0, 0, 0)")
self.put(f"return None")
def gen_alt(self, alt, rule, alt_index):
items = []
self.put(f"if (True")
with self.indent():
for i, item in enumerate(alt):
self.gen_item(item, items, alt_index, i)
self.put(f"):")
with self.indent():
self.put(f"self.show_index({alt_index}, 0, {len(alt)})")
self.put(f"return Node({rule.name!r}, [{', '.join(items)}])")
self.put(f"self.reset(pos)")
def gen_item(self, item, items, alt_index, item_index):
self.put(f"and self.show_index({alt_index}, {item_index})")
if item[0] in ('"', "'"):
self.put(f"and self.expect({item})")
else:
var = item.lower()
if var in items:
var += str(len(items))
items.append(var)
if item.isupper():
self.put(f"and ({var} := self.expect({item}))")
else:
self.put(f"and ({var} := self.{item}())")
def generate(rules, stream=None):
gen = Generator(stream)
gen.put(HEADER)
gen.put(f"class ToyParser(Parser):")
for rule in rules:
gen.put()
with gen.indent():
gen.gen_rule(rule)
|
