code: function() {
              var l = this.coeffs.length,
                  variable = this.variable;
              if(l === 0) return new core.Symbol(0);
              var end = l -1, str = '';
  
              for(var i=0; i<l; i++) {
                  //place the plus sign for all but the last one
                  var plus = i === end ? '' : '+',
                      e = this.coeffs[i];
                  if(!e.equals(0)) str += (e+'*'+variable+'^'+i+plus);
              }
              return _.parse(str);
          }
docs: Converts polynomial to Symbol
  @returns {Symbol}