javacc笔记3

void Input() :
  {}
  {
    "a" BC() "c"
  }

  void BC() :
  {}
  {
    "b" [ "c" ]
  }

有两种输出可能，如果：

void BC() :
  {}
  {
    "b"
    [ LOOKAHEAD( { getToken(1).kind == C && getToken(2).kind != C } )
      <C:"c">
    ]
  }

则

if (next token is "c" and following token is not "c") {
    choose the nested expansion (i.e., go into the [...] construct)
  } else {
    go beyond the [...] construct without entering it.
  }

rewritten 则：

void BC() :
  {}
  {
    "b"
    [ LOOKAHEAD( "c", { getToken(2).kind != C } )
      <C:"c">
    ]
  }