Re: [go-nuts] Pointer to the loop variable
Then turn vo into a Vertex variable, not a pointer
var vp Vertex = Vertex{}
...
if v.X == 3 {
vp = v
}
….
This time vp will be a copy of v,
Maybe you have to give some known values and exceptional case for your
domain, I mean, vp Vertex = { -1, -1} or any values your are
positive does not exists because maybe {0,0} is good data.
HTH
PS: You can break nested loops from an inside loop using break [label]
El martes, 10 de septiembre de 2019, 14:29:50 (UTC-5), Tong Sun escribió:
>
>
>
> On Tuesday, September 10, 2019 at 3:18:47 PM UTC-4, burak serdar wrote:
>>
>> On Tue, Sep 10, 2019 at 1:13 PM Tong Sun wrote:
>> >
>> > I'm experiencing a weird problem with my program and finally nail it
>> down to what exactly went wrong, so that I can write a minimum program to
>> duplicate it. See the following program:
>> >
>> > package main
>> >
>> >
>> > import (
>> > "fmt"
>> > )
>> >
>> >
>> > type Vertex struct {
>> > X int
>> > Y int
>> > }
>> >
>> >
>> > func main() {
>> > vs := []Vertex{
>> > Vertex{1, 2}, // has type Vertex
>> > Vertex{X: 3}, // Y:0 is implicit
>> > Vertex{}, // X:0 and Y:0
>> > }
>> >
>> >
>> > fmt.Printf("Vertex Slice %+v\n", vs)
>> > var vp *Vertex = nil
>> > for _, v := range vs {
>> > if v.X == 3 {
>> > vp =
>> > }
>> > }
>> > fmt.Printf("Found: %+v\n", vp)
>> > }
>> >
>> >
>> > https://play.golang.org/p/R645C5plojx
>> >
>> > I was expecting that the found Vertex is "v.X == 3", however the result
>> is not.
>>
>> Because you're keeping a pointer to the loop variable. v continues
>> changing after you store the address of it, so you get the latest
>> value of v. Instead, save a copy of v, or break the loop as soon as
>> what you're looking for is found:
>>
>
> I can't break the loop immediately as my not-minimized real program use a
> double loop to find the *closest *item. That's the reason I using the
> pointer to track my finding...
>
> if v.x==3 {
>>t:=v
>>vp=
>> }
>>
>
> OK. will do that. thx
>
> >
>> > - what exactly is causing the problem?
>> > - how to fix it so that I got what I was looking for?
>> >
>> > Again, the snip is at
>> > https://play.golang.org/p/R645C5plojx
>> >
>> > Thanks
>> >
>> > --
>> > You received this message because you are subscribed to the Google
>> Groups "golang-nuts" group.
>> > To unsubscribe from this group and stop receiving emails from it, send
>> an email to golan...@googlegroups.com.
>> > To view this discussion on the web visit
>> https://groups.google.com/d/msgid/golang-nuts/143205c1-2c86-4404-94d2-4182a6285e21%40googlegroups.com.
>>
>>
>>
>
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Re: [go-nuts] Pointer to the loop variable
On Tuesday, September 10, 2019 at 3:18:47 PM UTC-4, burak serdar wrote:
>
> On Tue, Sep 10, 2019 at 1:13 PM Tong Sun >
> wrote:
> >
> > I'm experiencing a weird problem with my program and finally nail it
> down to what exactly went wrong, so that I can write a minimum program to
> duplicate it. See the following program:
> >
> > package main
> >
> >
> > import (
> > "fmt"
> > )
> >
> >
> > type Vertex struct {
> > X int
> > Y int
> > }
> >
> >
> > func main() {
> > vs := []Vertex{
> > Vertex{1, 2}, // has type Vertex
> > Vertex{X: 3}, // Y:0 is implicit
> > Vertex{}, // X:0 and Y:0
> > }
> >
> >
> > fmt.Printf("Vertex Slice %+v\n", vs)
> > var vp *Vertex = nil
> > for _, v := range vs {
> > if v.X == 3 {
> > vp =
> > }
> > }
> > fmt.Printf("Found: %+v\n", vp)
> > }
> >
> >
> > https://play.golang.org/p/R645C5plojx
> >
> > I was expecting that the found Vertex is "v.X == 3", however the result
> is not.
>
> Because you're keeping a pointer to the loop variable. v continues
> changing after you store the address of it, so you get the latest
> value of v. Instead, save a copy of v, or break the loop as soon as
> what you're looking for is found:
>
I can't break the loop immediately as my not-minimized real program use a
double loop to find the *closest *item. That's the reason I using the
pointer to track my finding...
if v.x==3 {
>t:=v
>vp=
> }
>
OK. will do that. thx
>
> > - what exactly is causing the problem?
> > - how to fix it so that I got what I was looking for?
> >
> > Again, the snip is at
> > https://play.golang.org/p/R645C5plojx
> >
> > Thanks
> >
> > --
> > You received this message because you are subscribed to the Google
> Groups "golang-nuts" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> an email to golan...@googlegroups.com .
> > To view this discussion on the web visit
> https://groups.google.com/d/msgid/golang-nuts/143205c1-2c86-4404-94d2-4182a6285e21%40googlegroups.com.
>
>
>
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[go-nuts] Pointer to the loop variable
I'm experiencing a weird problem with my program and finally nail it down
to what exactly went wrong, so that I can write a minimum program to
duplicate it. See the following program:
package main
import (
"fmt"
)
type Vertex struct {
X int
Y int
}
func main() {
vs := []Vertex{
Vertex{1, 2}, // has type Vertex
Vertex{X: 3}, // Y:0 is implicit
Vertex{}, // X:0 and Y:0
}
fmt.Printf("Vertex Slice %+v\n", vs)
var vp *Vertex = nil
for _, v := range vs {
if v.X == 3 {
vp =
}
}
fmt.Printf("Found: %+v\n", vp)
}
https://play.golang.org/p/R645C5plojx
I was expecting that the found Vertex is "v.X == 3", however the result is
not.
- what exactly is causing the problem?
- how to fix it so that I got what I was looking for?
Again, the snip is at
https://play.golang.org/p/R645C5plojx
Thanks
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