ダイス式の構文

DiceCommand.txt

DiceCommand:
  Expression '='
  Expression '<'
  Expression '>'
  Expression '<='
  Expression '>='

Expression: 
  Term
  Expression '+' Term
  Expression '-' Term

Term:
  Factor
  Term '*' Factor
  Term '/' Factor

Factor:
  Numeric
  '(' Expression ')'
  '-' Factor
  DiceFactor

Numeric:
  [0-9]+

DiceFactor:
  'd'
  'd' Factor
  Factor 'd'
  Factor 'd' Factor

Parser.js

import Parsimmon, { alt, any, digits, eof, regex, seq, string, lazy } from 'parsimmon';

export let
    DiceText,
    DiceCommand,
    DiceExpression,
    Term,
    Factor,
    DiceFactor;

let plus = string('+');
let minus = string('-');
let mul = string('*');
let div = string('/');
let lparen = string('(');
let rparen = string(')');
let d = string('d');
let equal = string('=');
let lt = string('<');
let gt = string('>');
let le = string('<=');
let ge = string('>=');

DiceText = lazy(function() {
    return seq(
        alt(DiceCommand, any),
        eof
    );
});

DiceCommand = lazy(function() {
    return alt(
        seq(DiceExpression, equal),
        seq(DiceExpression, ge, DiceExpression),
        seq(DiceExpression, le, DiceExpression),
        seq(DiceExpression, gt, DiceExpression),
        seq(DiceExpression, lt, DiceExpression)
    );
});

DiceExpression = lazy(function () {
    return seq(Term, seq(alt(plus, minus), Term).many());
});

Factor = alt(
    seq(plus, DiceExpression),
    seq(minus, DiceExpression),
    seq(lparen, DiceExpression, rparen),
    digits.map(function(x) { return parseInt(x); }),
);

DiceFactor = alt(
    seq(Factor, d, Factor),
    seq(Factor, d),
    seq(d, Factor),
    d
);

Term = alt(
    seq(Factor, mul, Factor),
    seq(Factor, div, Factor),
    DiceFactor,
    Factor
);