Peggy proposition: Tagged template parser with auto-vectorization of template arguments

tagged-vector-adder.pegjs

import peg from "peggy-tag";

const PLACEHOLDER = "{{{ARG}}}";

const parse = peg`
{{
  function add(left, right) {
    if (typeof left === 'number') {
      if (typeof right === 'number') {
        return left + right;
      } else {
        return right.map(r => left + r);
      }
    } else {
      if (typeof right === 'number') {
        return left.map(l => l + right);
      } else {
        return left.map((l, i) => l + right[i]);
      }
    }
  }
}}

Start
  = Expression

Expression
  = left: Value '+' right: Value { return add(left, right); }

Value
  = Int
  / FormattedTemplateArgument

Int
  = [0-9]+ { return parseInt(text(), 10); }

FormattedTemplateArgument
   = "${PLACEHOLDER}" {
    const arg = options.args[offset()];
    return typeof arg === 'number' ? arg : new Float64Array(arg)
  }
`;

function p(strings, ...values) {
  let text = "";
  const args = {};
  strings.forEach((string, i) => {
    text += string;
    if (i < values.length) {
      args[text.length] = values[i];
      text += PLACEHOLDER;
    }
  });
  return parse(text, { args });
}
console.log(p`${6}+${[2, 3]}`);