buff = ["a","b","a"]
rule = token(/\w/)/:x - token("b") - backref(:x) >> proc{|x| x}
assert_equal(["a","b","a"], rule.parse(buff))
より文法っぽく書くとこんな感じ。
parser = TDParser.define{|g|
g.char = /\w/
g.word = g.char/:x - g.char - backref(:x) >> proc{|x| x}
}
parser.parse(buff)
