Calculus.js
function(integral, vars, point) {
                try {
                    return _.parse(integral, vars);
                }
                catch(e) {
                    //it failed for some reason so return the limit
                    return __.Limit.limit(integral, dx, point);
                }
            }
function(integral, vars, point) {
                try {
                    return _.parse(integral, vars);
                }
                catch(e) {
                    //it failed for some reason so return the limit
                    return __.Limit.limit(integral, dx, point);
                }
            }
function ( integral , vars , point ) { try { return _ . parse ( integral , vars ) ; } catch ( e ) { //it failed for some reason so return the limit
 return __ . Limit . limit ( integral , dx , point ) ; } }
make x the default variable of integration
make x the default variable of integration