Reputation: 677
I am working with golang's pointers the way I did with c++, but it seems not to work, which would be the right way to do it? or what am I doing wrong?, Thanks.
ftw I'm doing AsyncBinaryTrees.
type Obj interface {
Compare(node Obj) int
}
type Tree struct {
Item Obj
Rigth, Left *Tree
height int16
}
func Insert(t *Tree, item Obj) chan struct{} {
done := make(chan struct{}, 1)
go insert(t, item, done)
return done
}
func insert(t *Tree, item Obj, done chan struct{}) {
if t == nil {
t = &Tree{Item: nil, Rigth: nil, Left: nil, height: 0}
var signal struct{}
done <- signal
close(done)
} else {
if t.Item.Compare(item) == 1 { //Left
insert(t.Left, item, done)
} else if t.Item.Compare(item) == -1 { //Rigth
insert(t.Right, item, done)
} else {
close(done)
panic
}
}
}
//=== testing
func assertSignal(ch_signal chan struct{}, t *testing.T) {
_, done := <-ch_signal
if !done {
t.Error("Error: it should send a signal of empty struct")
}
}
func TestInsertion(t *testing.T) {
var tree *Tree
ch_signal := Insert(tree, newObjInt())
fmt.PrintLn(t) //=> <nil>
assertSignal(ch_signal, t) //=>PASS
ch_signal = Insert(tree, newObjInt())
fmt.PrintLn(t) //=> <nil>
assertSignal(ch_signal, t) //=>PASS
ch_signal = Insert(tree, newObjInt())
fmt.PrintLn(t) //=> <nil>
assertSignal(ch_signal, t) //=>PASS
ch_signal = Insert(tree, newObjInt())
assertSignal(ch_signal, t) //=>PASS
}
nil
nil
nil
TEST PASS
Upvotes: 0
Views: 447
Reputation: 43949
In your insert
function you have:
func insert(t *Tree, item Obj, done chan struct{}) {
if t == nil {
t = &Tree{Item: nil, Rigth: nil, Left: nil, height: 0}
...
}
This updates the local variable t
, but will not change the variable passed in the calling scope since Go passes function parameters by value. So when you make the following call:
insert(t.Left, item, done)
if t.Left
is nil
, its value will not be changed by the function call. If you do want it to update the variable, you'll need to define the function argument as t **Tree
, change references to set *t
instead, and change the call to:
insert(&t.Left, item, done)
There is no equivalent to C++'s syntax for passing function arguments by reference: instead you need to be explicit when passing pointers.
Upvotes: 3