如何为我的数据库查询创建 PEG.js 模式 (X "AND" Y "AND" ...)

Question

到目前为止我的解析器看起来像这样。

const parser = peg.generate(`

eq
  = left:attribute "=" right:value { return left == right; }

and
  = left:eq "AND" right:eq { return left && right; }

它能够读取像 id = 2 AND createdOn = 193242 这样的查询。我希望能够阅读 id = 2 AND secondId = 444 AND createdOn = 193242 等等...（任意数量的 "AND"）。如何通过 PEG.js 实现此目的？

Answer 1

应该这样做：

and
  = left:eq right:and_eq+ {
      if ( right.length === 1 ) return left && right;
      // handle more then 1 'AND eq' here
    }

and_eq
  = "AND" e:eq { return e; }

具有任意优先级的任意数量运算符的通用解决方案（创建 AST）：

{
function leftAssotiative(left, tail) {
  let r = left;
  for (let i = 0; i < tail.length; ++i) {
    r = { kind: tail[i][0], left: r, right: tail[i][1] };
  }
  return r;
}
function rightAssotiative(left, tail) {
  if (tail.length > 1) {
    let r = tail[tail.length-1][1];
    for (let i = tail.length-2; i >= 0; --i) {
      r = { kind: tail[i+1][0], left: tail[i][1], right: r };
    }
    return { kind: tail[0][0], left: left, right: r };
  }
  return left;
}
}

// Expressions
Expr// minimal priority
  = l:Expr0 t:(p0 Expr0)* { return rightAssotiative(l, t); };
Expr0
  = l:Expr1 t:(p1 Expr1)* { return leftAssotiative(l, t); };
...
ExprN// maximal priority
  = '(' @Expr ')';

// Operators
p0 = [+-];
p1 = [*/];
...

如何为我的数据库查询创建 PEG.js 模式 (X "AND" Y "AND" ...)

How can I create a PEG.js pattern for my DB queries (X "AND" Y "AND" ...)

javascript

pattern-matching

peg

typescript