calc-no-assoc.g.js

calc-no-assoc.g.js

/**
 * Explicit handling of the operator associativity. See also implicit handling
 * https://gist.github.com/DmitrySoshnikov/ab6ed4d41505c579cee9af759e77ead9
 *
 * Calculator grammar for a parser in Python.
 *
 * syntax-cli -g calc-no-assoc.g.js -m LALR1 -o calcparser.py
 *
 * >>> import calcparser
 * >>> calcparser.parse('2 + 2 * 2')
 * >>> 6
 */

{
  "lex": {
    "rules": [
      ["\\s+",        "# skip whitespace"],
      ["\\d+",        "return 'NUMBER'"],
      ["\\*",         "return '*'"],
      ["\\+",         "return '+'"],
      ["\\(",         "return '('"],
      ["\\)",         "return ')'"],
    ]
  },

  "bnf": {
    "E": [["E + T",   "$$ = $1 + $3"],
          ["T",       "$$ = $1"]],

    "T": [["T * F",   "$$ = $1 * $3"],
          ["F",       "$$ = $1"]],

    "F": [["NUMBER",  "$$ = int($1)"],
          ["( E )",   "$$ = $2"]],
  }
}