moved all math functions and operators to funcalls

So now if you want to add a new operator or math function all you have
to do is to add it to func.go. Conpletion will be generated from it.

util.go

@@ -17,7 +17,11 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 package main
 
-import "math"
+import (
+	"fmt"
+	"math"
+	"strings"
+)
 
 // find an item in a list
 func contains(s []string, e string) bool {
@@ -55,3 +59,7 @@ func const2num(name string) float64 {
 		return 0
 	}
 }
+
+func list2str(list Numbers) string {
+	return strings.Trim(strings.Join(strings.Fields(fmt.Sprint(list)), " "), "[]")
+}