Literal.js

A literal is either a variable, then called positive literal, or the negation of a variable, then called negative literal.

Source code

Constructor - takes a variable and a boolean as input.

function Literal(aVariable, negation) {

	'use strict';

the variable associated to this literal.

    var variable = aVariable;

true if this is a negative literal.

    var neg = negation;

true if the variable implements the equals function.

    var hasEquals = typeof variable.equals === 'function';

Returns true if this is a negative literal, false if this is a positive literal.

    this.isNegative = function() {
        return neg;
    };

Returns true if this is a positive literal, false if this is a negative literal.

    this.isPositive = function() {
        return !this.isNegative();
    };

Returns the variable associated to this literal.

    this.variable = function() {
        return variable;
    };

Returns true if o and this literal are equals:

this and other literal are of the same kind - i.e. both negative or positive
this and other literal associated variables are equals - using equals if available or === otherwise

    this.equals = function(o) {
        if (this.isNegative() === o.isNegative()) {
            if (hasEquals) {
                return variable.equals(o.variable());
            } else {
                return variable === o.variable();
            }
        } else {
            return false;
        }
    };

Evaluate the literal against the specified boolean value.

    this.evaluate = function(value) {
        if (negation) {
            return !value;
        } else {
            return value;
        }
    };
}

expose API to Node.js

module.exports = Literal;