two version of R2R are here HEAD master

1 files changed, 304 insertions, 0 deletions

diff --git a/.venv/lib/python3.12/site-packages/lark/parsers/lalr_analysis.py b/.venv/lib/python3.12/site-packages/lark/parsers/lalr_analysis.py
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+"""This module builds a LALR(1) transition-table for lalr_parser.py
+
+For now, shift/reduce conflicts are automatically resolved as shifts.
+"""
+
+# Author: Erez Shinan (2017)
+# Email : erezshin@gmail.com
+
+from collections import defaultdict
+
+from ..utils import classify, classify_bool, bfs, fzset, Enumerator, logger
+from ..exceptions import GrammarError
+
+from .grammar_analysis import GrammarAnalyzer, Terminal, LR0ItemSet
+from ..grammar import Rule
+
+###{standalone
+
+class Action:
+    def __init__(self, name):
+        self.name = name
+    def __str__(self):
+        return self.name
+    def __repr__(self):
+        return str(self)
+
+Shift = Action('Shift')
+Reduce = Action('Reduce')
+
+
+class ParseTable:
+    def __init__(self, states, start_states, end_states):
+        self.states = states
+        self.start_states = start_states
+        self.end_states = end_states
+
+    def serialize(self, memo):
+        tokens = Enumerator()
+        rules = Enumerator()
+
+        states = {
+            state: {tokens.get(token): ((1, arg.serialize(memo)) if action is Reduce else (0, arg))
+                    for token, (action, arg) in actions.items()}
+            for state, actions in self.states.items()
+        }
+
+        return {
+            'tokens': tokens.reversed(),
+            'states': states,
+            'start_states': self.start_states,
+            'end_states': self.end_states,
+        }
+
+    @classmethod
+    def deserialize(cls, data, memo):
+        tokens = data['tokens']
+        states = {
+            state: {tokens[token]: ((Reduce, Rule.deserialize(arg, memo)) if action==1 else (Shift, arg))
+                    for token, (action, arg) in actions.items()}
+            for state, actions in data['states'].items()
+        }
+        return cls(states, data['start_states'], data['end_states'])
+
+
+class IntParseTable(ParseTable):
+
+    @classmethod
+    def from_ParseTable(cls, parse_table):
+        enum = list(parse_table.states)
+        state_to_idx = {s:i for i,s in enumerate(enum)}
+        int_states = {}
+
+        for s, la in parse_table.states.items():
+            la = {k:(v[0], state_to_idx[v[1]]) if v[0] is Shift else v
+                  for k,v in la.items()}
+            int_states[ state_to_idx[s] ] = la
+
+
+        start_states = {start:state_to_idx[s] for start, s in parse_table.start_states.items()}
+        end_states = {start:state_to_idx[s] for start, s in parse_table.end_states.items()}
+        return cls(int_states, start_states, end_states)
+
+###}
+
+
+# digraph and traverse, see The Theory and Practice of Compiler Writing
+
+# computes F(x) = G(x) union (union { G(y) | x R y })
+# X: nodes
+# R: relation (function mapping node -> list of nodes that satisfy the relation)
+# G: set valued function
+def digraph(X, R, G):
+    F = {}
+    S = []
+    N = {}
+    for x in X:
+        N[x] = 0
+    for x in X:
+        # this is always true for the first iteration, but N[x] may be updated in traverse below
+        if N[x] == 0:
+            traverse(x, S, N, X, R, G, F)
+    return F
+
+# x: single node
+# S: stack
+# N: weights
+# X: nodes
+# R: relation (see above)
+# G: set valued function
+# F: set valued function we are computing (map of input -> output)
+def traverse(x, S, N, X, R, G, F):
+    S.append(x)
+    d = len(S)
+    N[x] = d
+    F[x] = G[x]
+    for y in R[x]:
+        if N[y] == 0:
+            traverse(y, S, N, X, R, G, F)
+        n_x = N[x]
+        assert(n_x > 0)
+        n_y = N[y]
+        assert(n_y != 0)
+        if (n_y > 0) and (n_y < n_x):
+            N[x] = n_y
+        F[x].update(F[y])
+    if N[x] == d:
+        f_x = F[x]
+        while True:
+            z = S.pop()
+            N[z] = -1
+            F[z] = f_x
+            if z == x:
+                break
+
+
+class LALR_Analyzer(GrammarAnalyzer):
+    def __init__(self, parser_conf, debug=False):
+        GrammarAnalyzer.__init__(self, parser_conf, debug)
+        self.nonterminal_transitions = []
+        self.directly_reads = defaultdict(set)
+        self.reads = defaultdict(set)
+        self.includes = defaultdict(set)
+        self.lookback = defaultdict(set)
+
+
+    def compute_lr0_states(self):
+        self.lr0_states = set()
+        # map of kernels to LR0ItemSets
+        cache = {}
+
+        def step(state):
+            _, unsat = classify_bool(state.closure, lambda rp: rp.is_satisfied)
+
+            d = classify(unsat, lambda rp: rp.next)
+            for sym, rps in d.items():
+                kernel = fzset({rp.advance(sym) for rp in rps})
+                new_state = cache.get(kernel, None)
+                if new_state is None:
+                    closure = set(kernel)
+                    for rp in kernel:
+                        if not rp.is_satisfied and not rp.next.is_term:
+                            closure |= self.expand_rule(rp.next, self.lr0_rules_by_origin)
+                    new_state = LR0ItemSet(kernel, closure)
+                    cache[kernel] = new_state
+
+                state.transitions[sym] = new_state
+                yield new_state
+
+            self.lr0_states.add(state)
+
+        for _ in bfs(self.lr0_start_states.values(), step):
+            pass
+
+    def compute_reads_relations(self):
+        # handle start state
+        for root in self.lr0_start_states.values():
+            assert(len(root.kernel) == 1)
+            for rp in root.kernel:
+                assert(rp.index == 0)
+                self.directly_reads[(root, rp.next)] = set([ Terminal('$END') ])
+
+        for state in self.lr0_states:
+            seen = set()
+            for rp in state.closure:
+                if rp.is_satisfied:
+                    continue
+                s = rp.next
+                # if s is a not a nonterminal
+                if s not in self.lr0_rules_by_origin:
+                    continue
+                if s in seen:
+                    continue
+                seen.add(s)
+                nt = (state, s)
+                self.nonterminal_transitions.append(nt)
+                dr = self.directly_reads[nt]
+                r = self.reads[nt]
+                next_state = state.transitions[s]
+                for rp2 in next_state.closure:
+                    if rp2.is_satisfied:
+                        continue
+                    s2 = rp2.next
+                    # if s2 is a terminal
+                    if s2 not in self.lr0_rules_by_origin:
+                        dr.add(s2)
+                    if s2 in self.NULLABLE:
+                        r.add((next_state, s2))
+
+    def compute_includes_lookback(self):
+        for nt in self.nonterminal_transitions:
+            state, nonterminal = nt
+            includes = []
+            lookback = self.lookback[nt]
+            for rp in state.closure:
+                if rp.rule.origin != nonterminal:
+                    continue
+                # traverse the states for rp(.rule)
+                state2 = state
+                for i in range(rp.index, len(rp.rule.expansion)):
+                    s = rp.rule.expansion[i]
+                    nt2 = (state2, s)
+                    state2 = state2.transitions[s]
+                    if nt2 not in self.reads:
+                        continue
+                    for j in range(i + 1, len(rp.rule.expansion)):
+                        if not rp.rule.expansion[j] in self.NULLABLE:
+                            break
+                    else:
+                        includes.append(nt2)
+                # state2 is at the final state for rp.rule
+                if rp.index == 0:
+                    for rp2 in state2.closure:
+                        if (rp2.rule == rp.rule) and rp2.is_satisfied:
+                            lookback.add((state2, rp2.rule))
+            for nt2 in includes:
+                self.includes[nt2].add(nt)
+
+    def compute_lookaheads(self):
+        read_sets = digraph(self.nonterminal_transitions, self.reads, self.directly_reads)
+        follow_sets = digraph(self.nonterminal_transitions, self.includes, read_sets)
+
+        for nt, lookbacks in self.lookback.items():
+            for state, rule in lookbacks:
+                for s in follow_sets[nt]:
+                    state.lookaheads[s].add(rule)
+
+    def compute_lalr1_states(self):
+        m = {}
+        reduce_reduce = []
+        for state in self.lr0_states:
+            actions = {}
+            for la, next_state in state.transitions.items():
+                actions[la] = (Shift, next_state.closure)
+            for la, rules in state.lookaheads.items():
+                if len(rules) > 1:
+                    # Try to resolve conflict based on priority
+                    p = [(r.options.priority or 0, r) for r in rules]
+                    p.sort(key=lambda r: r[0], reverse=True)
+                    best, second_best = p[:2]
+                    if best[0] > second_best[0]:
+                        rules = [best[1]]
+                    else:
+                        reduce_reduce.append((state, la, rules))
+                if la in actions:
+                    if self.debug:
+                        logger.warning('Shift/Reduce conflict for terminal %s: (resolving as shift)', la.name)
+                        logger.warning(' * %s', list(rules)[0])
+                else:
+                    actions[la] = (Reduce, list(rules)[0])
+            m[state] = { k.name: v for k, v in actions.items() }
+
+        if reduce_reduce:
+            msgs = []
+            for state, la, rules in reduce_reduce:
+                msg = 'Reduce/Reduce collision in %s between the following rules: %s' % (la, ''.join([ '\n\t- ' + str(r) for r in rules ]))
+                if self.debug:
+                    msg += '\n    collision occurred in state: {%s\n    }' % ''.join(['\n\t' + str(x) for x in state.closure])
+                msgs.append(msg)
+            raise GrammarError('\n\n'.join(msgs))
+
+        states = { k.closure: v for k, v in m.items() }
+
+        # compute end states
+        end_states = {}
+        for state in states:
+            for rp in state:
+                for start in self.lr0_start_states:
+                    if rp.rule.origin.name == ('$root_' + start) and rp.is_satisfied:
+                        assert(not start in end_states)
+                        end_states[start] = state
+
+        _parse_table = ParseTable(states, { start: state.closure for start, state in self.lr0_start_states.items() }, end_states)
+
+        if self.debug:
+            self.parse_table = _parse_table
+        else:
+            self.parse_table = IntParseTable.from_ParseTable(_parse_table)
+
+    def compute_lalr(self):
+        self.compute_lr0_states()
+        self.compute_reads_relations()
+        self.compute_includes_lookback()
+        self.compute_lookaheads()
+        self.compute_lalr1_states()