์ง๋ฌธ
์ง๊ธ๊น์ง ๋ด ํ์๋ ๋ค์๊ณผ ๊ฐ์ต๋๋ค.
const parser = peg.generate(`
eq
= left:attribute "=" right:value { return left == right; }
and
= left:eq "AND" right:eq { return left && right; }
id = 2 AND createdOn = 193242
์ ๊ฐ์ ์ฟผ๋ฆฌ๋ฅผ ์ฝ์ ์ ์์ต๋๋ค. ๋๋ id = 2 AND secondId = 444 AND createdOn = 193242
๋ฑ์ ์ฝ์ ์ ์๊ธฐ๋ฅผ ์ํฉ๋๋ค... ("AND"์ ์). PEG.js๋ฅผ ํตํด ์ด๋ป๊ฒ ์ด๋ฅผ ๋ฌ์ฑํ ์ ์์ต๋๊น?
์ด๋ ๊ฒ ํด์ผ ํฉ๋๋ค.
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; }
์ฐ์ ์์์ ๊ด๊ณ์์ด ์ฌ๋ฌ ์ฐ์ฐ์์ ๋ํ ์ผ๋ฐ ์๋ฃจ์ (AST ์์ฑ):
{
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
= '(' <strong i="6">@Expr</strong> ')';
// Operators
p0 = [+-];
p1 = [*/];
...
@futagoza ์น์ํ ๋๋. ๊ฐ์ฌ!