javascript - PEGJS:如何传递语法

Question

引自PEGJS Tutorial :

To generate a parser, call the PEG.buildParser method and pass your grammar as a parameter:

var parser = PEG.buildParser("start = ('a' / 'b')+");

我的语法有点复杂:

start
  = additive

additive
  = left:multiplicative "+" right:additive { return left + right; }
  / multiplicative

multiplicative
  = left:primary "*" right:multiplicative { return left * right; }
  / primary

primary
  = integer
  / "(" additive:additive ")" { return additive; }

integer "integer"
  = digits:[0-9]+ { return parseInt(digits.join(""), 10); }

我应该将语法的起始规则传递给 PEG.buildParser，即 additive，但我无法正确处理。如果我写PEG.buildParser(additive) 或 PEG.buildParser(start)，FireBug 说SyntaxError: 应为“=”或字符串，但已找到输入结尾；如果我写 PEG.buildParser(start = additive)，我会得到 GrammarError: Referenced rule "additive"does not exist；传递我的语法的正确方法是什么？

Answer 1

完整的语法必须作为字符串解析到buildParser，例如

PEG = require('pegjs');
var parser = PEG.buildParser(
  'start\n' +
  '  = additive\n' +
  '\n' +
  'additive\n' +
  '  = left:multiplicative "+" right:additive { return left + right; }\n' +
  '  / multiplicative\n' +
  '\n' +
  'multiplicative\n' +
  '  = left:primary "*" right:multiplicative { return left * right; }\n' +
  '  / primary\n' +
  '\n' +
  'primary\n' +
  '  = integer\n' +
  '  / "(" additive:additive ")" { return additive; }\n' +
  '\n' +
  'integer "integer"\n' +
  '  = digits:[0-9]+ { return parseInt(digits.join(""), 10); }'
);
console.log(parser.parse('(1+2)*3'));