made errors more explicit

errorTypes.go

@@ -1,26 +1,30 @@
 package sorted
 
+import (
+	"fmt"
+	"gitlab.com/Pixdigit/uniqueID"
+)
+
 //List is empty
 type ErrListEmpty struct {
-	S string
 }
 
 func (err ErrListEmpty) Error() string {
-	return err.S
+	return "list is empty"
 }
 
 type ErrDuplicateElem struct {
-	S string
+	DuplicateID uniqueID.ID
 }
 
 func (err ErrDuplicateElem) Error() string {
-	return err.S
+	return fmt.Sprint("Duplicate element with ID = ", err.DuplicateID)
 }
 
 type ErrNoElem struct {
-	S string
+	MissingID uniqueID.ID
 }
 
 func (err ErrNoElem) Error() string {
-	return err.S
+	return fmt.Sprint("no element with ID =", err.MissingID)
 }

list.go

@@ -41,7 +41,7 @@ func (sl *List) Insert(elem interface{}, value Num) {
 func (sl *List) Nearest(value Num) (interface{}, error) {
 
 	if len(sl.elems) == 0 {
-		return listElem{}, &ErrListEmpty{"List has no nearest element"}
+		return listElem{}, &ErrListEmpty{}
 	}
 
 	if sl.elems[0].value > value {

set.go

@@ -30,7 +30,7 @@ func (se *setElem) ID() uniqueID.ID {
 func (s *Set) Insert(uElem uniqueElem, value Num) error {
 	for _, elem := range s.elems {
 		if elem.ID() == uElem.ID() {
-			return &ErrDuplicateElem{"element already present in set"}
+			return &ErrDuplicateElem{elem.ID()}
 		}
 	}
 
@@ -70,13 +70,13 @@ func (s *Set) SetValue(ID uniqueID.ID, value Num) error {
 			return nil
 		}
 	}
-    return ErrNoElem{"the list has no item with that ID"}
+	return ErrNoElem{ID}
 }
 
 func (s *Set) Nearest(value Num) (interface{}, error) {
 
 	if len(s.elems) == 0 {
-		return setElem{}, &ErrListEmpty{"List has no nearest element"}
+		return setElem{}, &ErrListEmpty{}
 	}
 
 	if s.elems[0].value > value {

set_test.go

@@ -68,13 +68,13 @@ func TestSetValue(t *testing.T) {
 	err = set.Insert(d, 5);	if err != nil {tools.WrapErr(err, "could not insert test element", t)}
 	err = set.Insert(e, 4);	if err != nil {tools.WrapErr(err, "could not insert test element", t)}
 
-    set.SetValue(a.ID(), 3.5)
-    set.SetValue(e.ID(), -2)
-
-    tools.Test(set.Elems()[0] == e, "did not correctly change position when set new value", t)
-    tools.Test(set.Elems()[1] == b, "did not correctly change position when set new value", t)
-    tools.Test(set.Elems()[2] == c, "did not correctly change position when set new value", t)
-    tools.Test(set.Elems()[3] == a, "did not correctly change position when set new value", t)
-    tools.Test(set.Elems()[4] == d, "did not correctly change position when set new value", t)
+	set.SetValue(a.ID(), 3.5)
+	set.SetValue(e.ID(), -2)
+
+	tools.Test(set.Elems()[0] == e, "did not correctly change position when set new value", t)
+	tools.Test(set.Elems()[1] == b, "did not correctly change position when set new value", t)
+	tools.Test(set.Elems()[2] == c, "did not correctly change position when set new value", t)
+	tools.Test(set.Elems()[3] == a, "did not correctly change position when set new value", t)
+	tools.Test(set.Elems()[4] == d, "did not correctly change position when set new value", t)
 
 }