is it possible to overload arithmetic operators to support own bigint objects?

[mgttt]

dear, is it possible to overload the operators to support own bigint? e. g.
parse("a**b%c", {a:new BN("123456789"),b:new BN("654321"),c:new BN("76584")})

[silentmatt]

Yes, you can although you'll need to be careful how you handle numeric literals in the expression, since those will be parsed as native JavaScript numbers. The Parser class has a couple properties that provide the implementation for the various built-in operators and functions. You can replace those with your own implementation, or add/remove functions. Here's a quick made-up example that should give you an idea. You can look at the Parser constructor for the full list of operators and functions.

var parser = new Parser();

// Note that the exponentiation operator is ^, not **
parser.binaryOps['^'] = function (a, b) {
    // Convert JavaScript numbers to big integers
    if (!BN.isBN(a)) {
        a = new BN(a);
    }
    if (!BN.isBN(b)) {
        b = new BN(b);
    }
    return a.pow(b);
};

parser.binaryOps['%'] = function (a, b) {
    if (!BN.isBN(a)) {
        a = new BN(a);
    }
    if (!BN.isBN(b)) {
        b = new BN(b);
    }
    return a.mod(b);
};

// etc. for unaryOps, binaryOps, ternaryOps, functions, and/or consts

var answer = parser.parse("a^b%c", {a:new BN("123456789"),b:new BN("654321"),c:new BN("76584")}).evaluate()