VimPlug/parso
1
0
Fork 0
mirror of https://github.com/davidhalter/parso.git synced 2026-01-10 13:32:46 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

Add some comments

Browse Source
This commit is contained in:
Dave Halter
2018-06-15 10:21:00 +02:00
parent 9d452ec66a
commit 24346a0d32
1 changed files with 24 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
parso/pgen2/pgen.py
View File

@@ -206,37 +206,44 @@ def _simplify_dfas(dfas):
def _make_dfas(start, finish):
# To turn an NFA into a DFA, we define the states of the DFA
# to correspond to *sets* of states of the NFA. Then do some
# state reduction. Let's represent sets as dicts with 1 for
# values.
# state reduction.
assert isinstance(start, NFAState)
assert isinstance(finish, NFAState)
def addclosure(state, base):
assert isinstance(state, NFAState)
if state in base:
def addclosure(nfa_state, base_nfa_set):
assert isinstance(nfa_state, NFAState)
if nfa_state in base_nfa_set:
return
base.add(state)
for nfa_arc in state.arcs:
base_nfa_set.add(nfa_state)
for nfa_arc in nfa_state.arcs:
if nfa_arc.label_or_string is None:
addclosure(nfa_arc.next, base)
addclosure(nfa_arc.next, base_nfa_set)
base = set()
addclosure(start, base)
states = [DFAState(start.from_rule, base, finish)]
base_nfa_set = set()
addclosure(start, base_nfa_set)
states = [DFAState(start.from_rule, base_nfa_set, finish)]
for state in states: # NB states grows while we're iterating
arcs = {}
# Find state transitions and store them in arcs.
for nfa_state in state.nfa_set:
for nfa_arc in nfa_state.arcs:
if nfa_arc.label_or_string is not None:
addclosure(nfa_arc.next, arcs.setdefault(nfa_arc.label_or_string, set()))
nfa_set = arcs.setdefault(nfa_arc.label_or_string, set())
addclosure(nfa_arc.next, nfa_set)
# Now create the dfa's with no None's in arcs anymore. All Nones have
# been eliminated and state transitions (arcs) are properly defined, we
# just need to create the dfa's.
for label_or_string, nfa_set in arcs.items():
for st in states:
if st.nfa_set == nfa_set:
for nested_state in states:
if nested_state.nfa_set == nfa_set:
# The DFA state already exists for this rule.
break
else:
st = DFAState(start.from_rule, nfa_set, finish)
states.append(st)
state.add_arc(st, label_or_string)
nested_state = DFAState(start.from_rule, nfa_set, finish)
states.append(nested_state)
state.add_arc(nested_state, label_or_string)
return states # List of DFAState instances; first one is start