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Improve ParserGenerator readability #29

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b2283a5
Early continue allows less indentation, more readability
djc Jun 8, 2014
f87a8f5
Early continue allows less indentation, more readability
djc Jun 8, 2014
6c8ee46
Early continue allows less indentation, more readability
djc Jun 8, 2014
4d9003e
Early continue allows less indentation, more readability
djc Jun 8, 2014
c71c3bb
Early continue allows less indentation, more readability
djc Jun 8, 2014
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128 changes: 70 additions & 58 deletions rply/parsergenerator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -316,74 +316,86 @@ def from_grammar(cls, grammar):
st_goto = {}
for p in I:
if p.getlength() == p.lr_index + 1:

if p.name == "S'":
# Start symbol. Accept!
st_action["$end"] = 0
st_actionp["$end"] = p
else:
laheads = p.lookaheads[st]
for a in laheads:
if a in st_action:
r = st_action[a]
if r > 0:
sprec, slevel = grammar.productions[st_actionp[a].number].prec
rprec, rlevel = grammar.precedence.get(a, ("right", 0))
if (slevel < rlevel) or (slevel == rlevel and rprec == "left"):
st_action[a] = -p.number
st_actionp[a] = p
if not slevel and not rlevel:
sr_conflicts.append((st, repr(a), "reduce"))
grammar.productions[p.number].reduced += 1
elif not (slevel == rlevel and rprec == "nonassoc"):
if not rlevel:
sr_conflicts.append((st, repr(a), "shift"))
elif r < 0:
oldp = grammar.productions[-r]
pp = grammar.productions[p.number]
if oldp.number > pp.number:
st_action[a] = -p.number
st_actionp[a] = p
chosenp, rejectp = pp, oldp
grammar.productions[p.number].reduced += 1
grammar.productions[oldp.number].reduced -= 1
else:
chosenp, rejectp = oldp, pp
rr_conflicts.append((st, repr(chosenp), repr(rejectp)))
else:
raise ParserGeneratorError("Unknown conflict in state %d" % st)
else:
continue

laheads = p.lookaheads[st]
for a in laheads:

if a not in st_action:
st_action[a] = -p.number
st_actionp[a] = p
grammar.productions[p.number].reduced += 1
continue

r = st_action[a]
if r > 0:
sprec, slevel = grammar.productions[st_actionp[a].number].prec
rprec, rlevel = grammar.precedence.get(a, ("right", 0))
if (slevel < rlevel) or (slevel == rlevel and rprec == "left"):
st_action[a] = -p.number
st_actionp[a] = p
if not slevel and not rlevel:
sr_conflicts.append((st, repr(a), "reduce"))
grammar.productions[p.number].reduced += 1
elif not (slevel == rlevel and rprec == "nonassoc"):
if not rlevel:
sr_conflicts.append((st, repr(a), "shift"))
elif r < 0:
oldp = grammar.productions[-r]
pp = grammar.productions[p.number]
if oldp.number > pp.number:
st_action[a] = -p.number
st_actionp[a] = p
chosenp, rejectp = pp, oldp
grammar.productions[p.number].reduced += 1
grammar.productions[oldp.number].reduced -= 1
else:
chosenp, rejectp = oldp, pp
rr_conflicts.append((st, repr(chosenp), repr(rejectp)))
else:
raise ParserGeneratorError("Unknown conflict in state %d" % st)

else:

i = p.lr_index
a = p.prod[i + 1]
if a in grammar.terminals:
g = cls.lr0_goto(I, a, add_count, goto_cache)
j = cidhash.get(g, -1)
if j >= 0:
if a in st_action:
r = st_action[a]
if r > 0:
if r != j:
raise ParserGeneratorError("Shift/shift conflict in state %d" % st)
elif r < 0:
rprec, rlevel = grammar.productions[st_actionp[a].number].prec
sprec, slevel = grammar.precedence.get(a, ("right", 0))
if (slevel > rlevel) or (slevel == rlevel and rprec == "right"):
grammar.productions[st_actionp[a].number].reduced -= 1
st_action[a] = j
st_actionp[a] = p
if not rlevel:
sr_conflicts.append((st, repr(a), "shift"))
elif not (slevel == rlevel and rprec == "nonassoc"):
if not slevel and not rlevel:
sr_conflicts.append((st, repr(a), "reduce"))
else:
raise ParserGeneratorError("Unknown conflict in state %d" % st)
else:
st_action[a] = j
st_actionp[a] = p
if a not in grammar.terminals:
continue

g = cls.lr0_goto(I, a, add_count, goto_cache)
j = cidhash.get(g, -1)
if j < 0:
continue

if a not in st_action:
st_action[a] = j
st_actionp[a] = p
continue

r = st_action[a]
if r > 0:
if r != j:
raise ParserGeneratorError("Shift/shift conflict in state %d" % st)
elif r < 0:
rprec, rlevel = grammar.productions[st_actionp[a].number].prec
sprec, slevel = grammar.precedence.get(a, ("right", 0))
if (slevel > rlevel) or (slevel == rlevel and rprec == "right"):
grammar.productions[st_actionp[a].number].reduced -= 1
st_action[a] = j
st_actionp[a] = p
if not rlevel:
sr_conflicts.append((st, repr(a), "shift"))
elif not (slevel == rlevel and rprec == "nonassoc"):
if not slevel and not rlevel:
sr_conflicts.append((st, repr(a), "reduce"))
else:
raise ParserGeneratorError("Unknown conflict in state %d" % st)

nkeys = set()
for ii in I:
for s in ii.unique_syms:
Expand Down