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@subheader """\
from ast import literal_eval
from pegen.grammar import (
Alt,
Cut,
Gather,
Group,
Item,
Lookahead,
LookaheadOrCut,
MetaTuple,
MetaList,
NameLeaf,
NamedItem,
NamedItemList,
NegativeLookahead,
Opt,
Plain,
PositiveLookahead,
Repeat0,
Repeat1,
Rhs,
Rule,
RuleList,
RuleName,
Grammar,
StringLeaf,
)
"""
start[Grammar]: grammar ENDMARKER { grammar }
grammar[Grammar]:
| metas rules { Grammar(rules, metas) }
| rules { Grammar(rules, []) }
metas[MetaList]:
| meta metas { [meta] + metas }
| meta { [meta] }
meta[MetaTuple]:
| "@" NAME NEWLINE { (name.string, None) }
| "@" a=NAME b=NAME NEWLINE { (a.string, b.string) }
| "@" NAME STRING NEWLINE { (name.string, literal_eval(string.string)) }
rules[RuleList]:
| rule rules { [rule] + rules }
| rule { [rule] }
rule[Rule]:
| rulename memoflag? ":" alts NEWLINE INDENT more_alts DEDENT {
Rule(rulename[0], rulename[1], Rhs(alts.alts + more_alts.alts), memo=opt) }
| rulename memoflag? ":" NEWLINE INDENT more_alts DEDENT {
Rule(rulename[0], rulename[1], more_alts, memo=opt) }
| rulename memoflag? ":" alts NEWLINE { Rule(rulename[0], rulename[1], alts, memo=opt) }
rulename[RuleName]:
| NAME '[' type=NAME '*' ']' { (name.string, type.string+"*") }
| NAME '[' type=NAME ']' { (name.string, type.string) }
| NAME { (name.string, None) }
# In the future this may return something more complicated
memoflag[str]:
| '(' 'memo' ')' { "memo" }
alts[Rhs]:
| alt "|" alts { Rhs([alt] + alts.alts)}
| alt { Rhs([alt]) }
more_alts[Rhs]:
| "|" alts NEWLINE more_alts { Rhs(alts.alts + more_alts.alts) }
| "|" alts NEWLINE { Rhs(alts.alts) }
alt[Alt]:
| items '$' action { Alt(items + [NamedItem(None, NameLeaf('ENDMARKER'))], action=action) }
| items '$' { Alt(items + [NamedItem(None, NameLeaf('ENDMARKER'))], action=None) }
| items action { Alt(items, action=action) }
| items { Alt(items, action=None) }
items[NamedItemList]:
| named_item items { [named_item] + items }
| named_item { [named_item] }
named_item[NamedItem]:
| NAME '=' ~ item {NamedItem(name.string, item)}
| item {NamedItem(None, item)}
| it=lookahead {NamedItem(None, it)}
lookahead[LookaheadOrCut]:
| '&' ~ atom {PositiveLookahead(atom)}
| '!' ~ atom {NegativeLookahead(atom)}
| '~' {Cut()}
item[Item]:
| '[' ~ alts ']' {Opt(alts)}
| atom '?' {Opt(atom)}
| atom '*' {Repeat0(atom)}
| atom '+' {Repeat1(atom)}
| sep=atom '.' node=atom '+' {Gather(sep, node)}
| atom {atom}
atom[Plain]:
| '(' ~ alts ')' {Group(alts)}
| NAME {NameLeaf(name.string) }
| STRING {StringLeaf(string.string)}
# Mini-grammar for the actions
action[str]: "{" ~ target_atoms "}" { target_atoms }
target_atoms[str]:
| target_atom target_atoms { target_atom + " " + target_atoms }
| target_atom { target_atom }
target_atom[str]:
| "{" ~ target_atoms "}" { "{" + target_atoms + "}" }
| NAME { name.string }
| NUMBER { number.string }
| STRING { string.string }
| "?" { "?" }
| ":" { ":" }
| !"}" OP { op.string }