Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread Victor Giordano 
Thanks for sharing point the view!. And you can bet that i done that!!! :D
It was quite a challenge you know!! In nowadays system is working, let keep
crossing fingers please...

El sáb., 26 ene. 2019 a las 18:45, robert engels ()
escribió:

> Yes, and you can do that.
>
> On Jan 26, 2019, at 3:36 PM, Victor Giordano 
> wrote:
>
> Probably i need to reveal the underlying problem i was trying to solve
>
> At a glande: an appoinment subsystem for a health *organization*,
> considering practitioners that work on *services *offering *practices *that
> refers to *billables *items, the *practices *may need one or more
> *equipment*, also taking into accountg the  *practitioners* *availability*
> expressed in relative periodic terms (weekly for example) and absoulte
> terms (a given day on the cosmos) and their holidays, and the *location *where
> the patient-doctor encounter will occur, also consdiering the *center *(a
> heath *organization *has one or many) holidays.
>
> So  need to resolve availabiltiies to determine when a given practice can
> be performe. I have several structs represeting the entties involved in the
> process (the one marked in *bold*), for each one of these structs there
> is a *theorical availbility* and a *actual usage* that leads you to
> calculate the *actual availlity*, so *everything related to the
> availabilty of these enties need to be placed somewhere*, so my original
> idea was to associate each algoritm with the struct but without writing the
> algorithms as part of the struct, a map comes in handy here.
>
>
> El sáb., 26 ene. 2019 a las 16:31, Wagner Riffel ()
> escribió:
>
>> i don't quite understand why you're using enums as keys, you can use a
>> anything but what already was pointed out, following your person example:
>> https://play.golang.org/p/cuMlPeqR7Qb
>>
>>
>> On Sat, Jan 26, 2019, 3:26 PM Victor Giordano 
>> wrote:
>>
>>> Yup! That's right! At the end of the day i used the enums idioms
>>> ,
>>> employing integer type (the value that supports the "enum" )
>>>
>>> (TL;DR;) Ancient History :
>>>
>>> The problem arises as i get used to use maps in Java where you can use
>>> as a key a class definition (that is custom data type in Java, like the
>>> same way an "struct" in Golang is a custom data type). So i get use to work
>>> with types as keys, that way i could associate logic and data with an
>>> asbtraction (recall that logic and data does not intrinsically belong to
>>> that abstraction, so it would be wrong to place all in there).
>>>
>>> I wake-up in golang without that capability: i mean how i may refer to a
>>> group of well know struct definitions in a generic way, i mean for example
>>> this:
>>>
>>> type Person struct {
>>> }
>>>
>>> var SpanishTermByStruct map[struct]string = map[struct]string{
>>> Person: "person",
>>> }
>>>
>>> ? and in that moment the wondering about using "type" for key (or value)
>>> comes to my mind... i then i get that is not allowed.
>>>
>>>
>>> El sáb., 26 ene. 2019 a las 10:57,  escribió:
>>>
 I looked at your program example, mainly using the reflection type to
 design the mapped key, perhaps the reflected key is a comparable type, but
 I mainly propose specific types, such as func, slice, map can not be used
 as a key use

 在 2019年1月25日星期五 UTC+8下午11:31:57，Victor Giordano写道：
>
> Yeah, i got the idea. I had already researched about it and what you
> can do about it.
> 
> I was only repeating what i want as a dev in this community!
>
> El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel
> escribió:
>>
>> you can "employ" any custom type as key but the ones that doesn't
>> defines equality operations, see
>> https://golang.org/ref/spec#Comparison_operators
>> as Ian already pointed out, you just can't build your custom type on
>> top of func, map or slice to be a valid key, anything else you can.
>>
>> On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano 
>> wrote:
>> >
>> > Just wanna say : It would be nice to employ a custom type as a
>> valid key for a map!!! :D
>> >
>> >
>> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com
>> escribió:
>> >>
>> >> thanks lan.
>> >>
>> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
>> >>>
>> >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote:
>> >>> >
>> >>> > i got :
>> >>> >   # command-line-arguments
>> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be
>> compared to nil)
>> >>>
>> >>> Yes, that is what the language spec says and it is what I said:
>> in Go,
>> >>> function values are not comparable.
>> >>>
>> >>> I wrote that code as an example to help explain why function
>> values

Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread robert engels 
Yes, and you can do that.

> On Jan 26, 2019, at 3:36 PM, Victor Giordano  wrote:
> 
> Probably i need to reveal the underlying problem i was trying to solve 
> 
> At a glande: an appoinment subsystem for a health organization, considering 
> practitioners that work on services offering practices that refers to 
> billables items, the practices may need one or more equipment, also taking 
> into accountg the  practitioners availability expressed in relative periodic 
> terms (weekly for example) and absoulte terms (a given day on the cosmos) and 
> their holidays, and the location where the patient-doctor encounter will 
> occur, also consdiering the center (a heath organization has one or many) 
> holidays.
> 
> So  need to resolve availabiltiies to determine when a given practice can be 
> performe. I have several structs represeting the entties involved in the 
> process (the one marked in bold), for each one of these structs there is a 
> theorical availbility and a actual usage that leads you to calculate the 
> actual availlity, so everything related to the availabilty of these enties 
> need to be placed somewhere, so my original idea was to associate each 
> algoritm with the struct but without writing the algorithms as part of the 
> struct, a map comes in handy here. 
> 
> 
> El sáb., 26 ene. 2019 a las 16:31, Wagner Riffel ( >) escribió:
> i don't quite understand why you're using enums as keys, you can use a 
> anything but what already was pointed out, following your person example:
> https://play.golang.org/p/cuMlPeqR7Qb 
> 
> 
> On Sat, Jan 26, 2019, 3:26 PM Victor Giordano  > wrote:
> Yup! That's right! At the end of the day i used the enums idioms 
> ,
>  employing integer type (the value that supports the "enum" )
> 
> (TL;DR;) Ancient History :
> 
> The problem arises as i get used to use maps in Java where you can use as a 
> key a class definition (that is custom data type in Java, like the same way 
> an "struct" in Golang is a custom data type). So i get use to work with types 
> as keys, that way i could associate logic and data with an asbtraction 
> (recall that logic and data does not intrinsically belong to that 
> abstraction, so it would be wrong to place all in there).
> 
> I wake-up in golang without that capability: i mean how i may refer to a 
> group of well know struct definitions in a generic way, i mean for example 
> this: 
> 
> type Person struct {
> }
> 
> var SpanishTermByStruct map[struct]string = map[struct]string{
>   Person: "person",
> }
> 
> ? and in that moment the wondering about using "type" for key (or value) 
> comes to my mind... i then i get that is not allowed.
> 
> 
> El sáb., 26 ene. 2019 a las 10:57,  > escribió:
> I looked at your program example, mainly using the reflection type to design 
> the mapped key, perhaps the reflected key is a comparable type, but I mainly 
> propose specific types, such as func, slice, map can not be used as a key use
> 
> 在 2019年1月25日星期五 UTC+8下午11:31:57，Victor Giordano写道：
> Yeah, i got the idea. I had already researched about it and what you can do 
> about it. 
> 
> I was only repeating what i want as a dev in this community! 
> 
> El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel escribió:
> you can "employ" any custom type as key but the ones that doesn't 
> defines equality operations, see 
> https://golang.org/ref/spec#Comparison_operators 
>  
> as Ian already pointed out, you just can't build your custom type on 
> top of func, map or slice to be a valid key, anything else you can. 
> 
> On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano > 
> wrote: 
> > 
> > Just wanna say : It would be nice to employ a custom type as a valid key 
> > for a map!!! :D 
> > 
> > 
> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com <> 
> > escribió: 
> >> 
> >> thanks lan. 
> >> 
> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道： 
> >>> 
> >>> On Tue, Jan 22, 2019 at 11:47 PM > wrote: 
> >>> > 
> >>> > i got : 
> >>> >   # command-line-arguments 
> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be compared 
> >>> > to nil) 
> >>> 
> >>> Yes, that is what the language spec says and it is what I said: in Go, 
> >>> function values are not comparable. 
> >>> 
> >>> I wrote that code as an example to help explain why function values 
> >>> are not comparable. 
> >>> 
> >>> Ian 
> >>> 
> >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com <>写道： 
> >>> >> 
> >>> >>  When i use the func, map slice as the key of map, it isn't work! 
> >>> >>  So  I lookup source  why, i find 
> >>> >> 
> >>> >> // spec: "The comparison

Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread Victor Giordano 
Probably i need to reveal the underlying problem i was trying to solve

At a glande: an appoinment subsystem for a health *organization*,
considering practitioners that work on *services *offering *practices *that
refers to *billables *items, the *practices *may need one or more
*equipment*, also taking into accountg the  *practitioners* *availability*
expressed in relative periodic terms (weekly for example) and absoulte
terms (a given day on the cosmos) and their holidays, and the *location *where
the patient-doctor encounter will occur, also consdiering the *center *(a
heath *organization *has one or many) holidays.

So  need to resolve availabiltiies to determine when a given practice can
be performe. I have several structs represeting the entties involved in the
process (the one marked in *bold*), for each one of these structs there is
a *theorical availbility* and a *actual usage* that leads you to calculate
the *actual availlity*, so *everything related to the availabilty of these
enties need to be placed somewhere*, so my original idea was to associate
each algoritm with the struct but without writing the algorithms as part of
the struct, a map comes in handy here.


El sáb., 26 ene. 2019 a las 16:31, Wagner Riffel ()
escribió:

> i don't quite understand why you're using enums as keys, you can use a
> anything but what already was pointed out, following your person example:
> https://play.golang.org/p/cuMlPeqR7Qb
>
>
> On Sat, Jan 26, 2019, 3:26 PM Victor Giordano 
> wrote:
>
>> Yup! That's right! At the end of the day i used the enums idioms
>> ,
>> employing integer type (the value that supports the "enum" )
>>
>> (TL;DR;) Ancient History :
>>
>> The problem arises as i get used to use maps in Java where you can use as
>> a key a class definition (that is custom data type in Java, like the same
>> way an "struct" in Golang is a custom data type). So i get use to work with
>> types as keys, that way i could associate logic and data with an
>> asbtraction (recall that logic and data does not intrinsically belong to
>> that abstraction, so it would be wrong to place all in there).
>>
>> I wake-up in golang without that capability: i mean how i may refer to a
>> group of well know struct definitions in a generic way, i mean for example
>> this:
>>
>> type Person struct {
>> }
>>
>> var SpanishTermByStruct map[struct]string = map[struct]string{
>> Person: "person",
>> }
>>
>> ? and in that moment the wondering about using "type" for key (or value)
>> comes to my mind... i then i get that is not allowed.
>>
>>
>> El sáb., 26 ene. 2019 a las 10:57,  escribió:
>>
>>> I looked at your program example, mainly using the reflection type to
>>> design the mapped key, perhaps the reflected key is a comparable type, but
>>> I mainly propose specific types, such as func, slice, map can not be used
>>> as a key use
>>>
>>> 在 2019年1月25日星期五 UTC+8下午11:31:57，Victor Giordano写道：

 Yeah, i got the idea. I had already researched about it and what you
 can do about it.
 
 I was only repeating what i want as a dev in this community!

 El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel
 escribió:
>
> you can "employ" any custom type as key but the ones that doesn't
> defines equality operations, see
> https://golang.org/ref/spec#Comparison_operators
> as Ian already pointed out, you just can't build your custom type on
> top of func, map or slice to be a valid key, anything else you can.
>
> On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano 
> wrote:
> >
> > Just wanna say : It would be nice to employ a custom type as a valid
> key for a map!!! :D
> >
> >
> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com
> escribió:
> >>
> >> thanks lan.
> >>
> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
> >>>
> >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote:
> >>> >
> >>> > i got :
> >>> >   # command-line-arguments
> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be
> compared to nil)
> >>>
> >>> Yes, that is what the language spec says and it is what I said: in
> Go,
> >>> function values are not comparable.
> >>>
> >>> I wrote that code as an example to help explain why function
> values
> >>> are not comparable.
> >>>
> >>> Ian
> >>>
> >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
> >>> >>
> >>> >>  When i use the func, map slice as the key of map, it isn't
> work!
> >>> >>  So  I lookup source  why, i find
> >>> >>
> >>> >> // spec: "The comparison operators == and != must be fully
> defined
> >>> >> // for operands of the key type; thus the key type must

Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread Wagner Riffel 
i don't quite understand why you're using enums as keys, you can use a
anything but what already was pointed out, following your person example:
https://play.golang.org/p/cuMlPeqR7Qb


On Sat, Jan 26, 2019, 3:26 PM Victor Giordano  wrote:

> Yup! That's right! At the end of the day i used the enums idioms
> ,
> employing integer type (the value that supports the "enum" )
>
> (TL;DR;) Ancient History :
>
> The problem arises as i get used to use maps in Java where you can use as
> a key a class definition (that is custom data type in Java, like the same
> way an "struct" in Golang is a custom data type). So i get use to work with
> types as keys, that way i could associate logic and data with an
> asbtraction (recall that logic and data does not intrinsically belong to
> that abstraction, so it would be wrong to place all in there).
>
> I wake-up in golang without that capability: i mean how i may refer to a
> group of well know struct definitions in a generic way, i mean for example
> this:
>
> type Person struct {
> }
>
> var SpanishTermByStruct map[struct]string = map[struct]string{
> Person: "person",
> }
>
> ? and in that moment the wondering about using "type" for key (or value)
> comes to my mind... i then i get that is not allowed.
>
>
> El sáb., 26 ene. 2019 a las 10:57,  escribió:
>
>> I looked at your program example, mainly using the reflection type to
>> design the mapped key, perhaps the reflected key is a comparable type, but
>> I mainly propose specific types, such as func, slice, map can not be used
>> as a key use
>>
>> 在 2019年1月25日星期五 UTC+8下午11:31:57，Victor Giordano写道：
>>>
>>> Yeah, i got the idea. I had already researched about it and what you
>>> can do about it.
>>> 
>>> I was only repeating what i want as a dev in this community!
>>>
>>> El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel
>>> escribió:

 you can "employ" any custom type as key but the ones that doesn't
 defines equality operations, see
 https://golang.org/ref/spec#Comparison_operators
 as Ian already pointed out, you just can't build your custom type on
 top of func, map or slice to be a valid key, anything else you can.

 On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano 
 wrote:
 >
 > Just wanna say : It would be nice to employ a custom type as a valid
 key for a map!!! :D
 >
 >
 > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com
 escribió:
 >>
 >> thanks lan.
 >>
 >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
 >>>
 >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote:
 >>> >
 >>> > i got :
 >>> >   # command-line-arguments
 >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be
 compared to nil)
 >>>
 >>> Yes, that is what the language spec says and it is what I said: in
 Go,
 >>> function values are not comparable.
 >>>
 >>> I wrote that code as an example to help explain why function values
 >>> are not comparable.
 >>>
 >>> Ian
 >>>
 >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
 >>> >>
 >>> >>  When i use the func, map slice as the key of map, it isn't
 work!
 >>> >>  So  I lookup source  why, i find
 >>> >>
 >>> >> // spec: "The comparison operators == and != must be fully
 defined
 >>> >> // for operands of the key type; thus the key type must
 not be a
 >>> >> // function, map, or slice."
 >>> >> //
 >>> >> // Delay this check because it requires fully setup
 types;
 >>> >> // it is safe to continue in any case (was issue 6667).
 >>> >> check.later(func() {
 >>> >> if !Comparable(typ.key) {
 >>> >> check.errorf(e.Key.Pos(), "invalid map key type
 %s", typ.key)
 >>> >> }
 >>> >> })
 >>> >> // Comparable reports whether values of type T are comparable.
 >>> >> func Comparable(T Type) bool {
 >>> >> switch t := T.Underlying().(type) {
 >>> >> case *Basic:
 >>> >> // assume invalid types to be comparable
 >>> >> // to avoid follow-up errors
 >>> >> return t.kind != UntypedNil
 >>> >> case *Pointer, *Interface, *Chan:
 >>> >> return true
 >>> >> case *Struct:
 >>> >> for _, f := range t.fields {
 >>> >> if !Comparable(f.typ) {
 >>> >> return false
 >>> >> }
 >>> >> }
 >>> >> return true
 >>> >> case *Array:
 >>> >> return Comparable(t.elem)
 >>> >> }
 >>> >> return false
 >>> >> }
 >>> >
 >>> > --
 >>> > You received this message

Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread Victor Giordano 
Yup! That's right! At the end of the day i used the enums idioms
,
employing integer type (the value that supports the "enum" )

(TL;DR;) Ancient History :

The problem arises as i get used to use maps in Java where you can use as a
key a class definition (that is custom data type in Java, like the same way
an "struct" in Golang is a custom data type). So i get use to work with
types as keys, that way i could associate logic and data with an
asbtraction (recall that logic and data does not intrinsically belong to
that abstraction, so it would be wrong to place all in there).

I wake-up in golang without that capability: i mean how i may refer to a
group of well know struct definitions in a generic way, i mean for example
this:

type Person struct {
}

var SpanishTermByStruct map[struct]string = map[struct]string{
Person: "person",
}

? and in that moment the wondering about using "type" for key (or value)
comes to my mind... i then i get that is not allowed.


El sáb., 26 ene. 2019 a las 10:57,  escribió:

> I looked at your program example, mainly using the reflection type to
> design the mapped key, perhaps the reflected key is a comparable type, but
> I mainly propose specific types, such as func, slice, map can not be used
> as a key use
>
> 在 2019年1月25日星期五 UTC+8下午11:31:57，Victor Giordano写道：
>>
>> Yeah, i got the idea. I had already researched about it and what you can
>> do about it.
>> 
>> I was only repeating what i want as a dev in this community!
>>
>> El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel escribió:
>>>
>>> you can "employ" any custom type as key but the ones that doesn't
>>> defines equality operations, see
>>> https://golang.org/ref/spec#Comparison_operators
>>> as Ian already pointed out, you just can't build your custom type on
>>> top of func, map or slice to be a valid key, anything else you can.
>>>
>>> On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano 
>>> wrote:
>>> >
>>> > Just wanna say : It would be nice to employ a custom type as a valid
>>> key for a map!!! :D
>>> >
>>> >
>>> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com
>>> escribió:
>>> >>
>>> >> thanks lan.
>>> >>
>>> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
>>> >>>
>>> >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote:
>>> >>> >
>>> >>> > i got :
>>> >>> >   # command-line-arguments
>>> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be
>>> compared to nil)
>>> >>>
>>> >>> Yes, that is what the language spec says and it is what I said: in
>>> Go,
>>> >>> function values are not comparable.
>>> >>>
>>> >>> I wrote that code as an example to help explain why function values
>>> >>> are not comparable.
>>> >>>
>>> >>> Ian
>>> >>>
>>> >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
>>> >>> >>
>>> >>> >>  When i use the func, map slice as the key of map, it isn't
>>> work!
>>> >>> >>  So  I lookup source  why, i find
>>> >>> >>
>>> >>> >> // spec: "The comparison operators == and != must be fully
>>> defined
>>> >>> >> // for operands of the key type; thus the key type must
>>> not be a
>>> >>> >> // function, map, or slice."
>>> >>> >> //
>>> >>> >> // Delay this check because it requires fully setup
>>> types;
>>> >>> >> // it is safe to continue in any case (was issue 6667).
>>> >>> >> check.later(func() {
>>> >>> >> if !Comparable(typ.key) {
>>> >>> >> check.errorf(e.Key.Pos(), "invalid map key type
>>> %s", typ.key)
>>> >>> >> }
>>> >>> >> })
>>> >>> >> // Comparable reports whether values of type T are comparable.
>>> >>> >> func Comparable(T Type) bool {
>>> >>> >> switch t := T.Underlying().(type) {
>>> >>> >> case *Basic:
>>> >>> >> // assume invalid types to be comparable
>>> >>> >> // to avoid follow-up errors
>>> >>> >> return t.kind != UntypedNil
>>> >>> >> case *Pointer, *Interface, *Chan:
>>> >>> >> return true
>>> >>> >> case *Struct:
>>> >>> >> for _, f := range t.fields {
>>> >>> >> if !Comparable(f.typ) {
>>> >>> >> return false
>>> >>> >> }
>>> >>> >> }
>>> >>> >> return true
>>> >>> >> case *Array:
>>> >>> >> return Comparable(t.elem)
>>> >>> >> }
>>> >>> >> return false
>>> >>> >> }
>>> >>> >
>>> >>> > --
>>> >>> > 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 golang-nuts...@googlegroups.com.
>>> >>> > For more options, visit https://groups.google.com/d/optout.
>>> >
>>> > --
>>> > You received this message because you are subscribed to the Google
>>> Groups "golang-nuts" group.

Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread mountainfpf 
I looked at your program example, mainly using the reflection type to 
design the mapped key, perhaps the reflected key is a comparable type, but 
I mainly propose specific types, such as func, slice, map can not be used 
as a key use

在 2019年1月25日星期五 UTC+8下午11:31:57，Victor Giordano写道：
>
> Yeah, i got the idea. I had already researched about it and what you can 
> do about it. 
> 
> I was only repeating what i want as a dev in this community! 
>
> El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel escribió:
>>
>> you can "employ" any custom type as key but the ones that doesn't 
>> defines equality operations, see 
>> https://golang.org/ref/spec#Comparison_operators 
>> as Ian already pointed out, you just can't build your custom type on 
>> top of func, map or slice to be a valid key, anything else you can. 
>>
>> On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano  
>> wrote: 
>> > 
>> > Just wanna say : It would be nice to employ a custom type as a valid 
>> key for a map!!! :D 
>> > 
>> > 
>> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com 
>> escribió: 
>> >> 
>> >> thanks lan. 
>> >> 
>> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道： 
>> >>> 
>> >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote: 
>> >>> > 
>> >>> > i got : 
>> >>> >   # command-line-arguments 
>> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be 
>> compared to nil) 
>> >>> 
>> >>> Yes, that is what the language spec says and it is what I said: in 
>> Go, 
>> >>> function values are not comparable. 
>> >>> 
>> >>> I wrote that code as an example to help explain why function values 
>> >>> are not comparable. 
>> >>> 
>> >>> Ian 
>> >>> 
>> >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道： 
>> >>> >> 
>> >>> >>  When i use the func, map slice as the key of map, it isn't 
>> work! 
>> >>> >>  So  I lookup source  why, i find 
>> >>> >> 
>> >>> >> // spec: "The comparison operators == and != must be fully 
>> defined 
>> >>> >> // for operands of the key type; thus the key type must 
>> not be a 
>> >>> >> // function, map, or slice." 
>> >>> >> // 
>> >>> >> // Delay this check because it requires fully setup types; 
>> >>> >> // it is safe to continue in any case (was issue 6667). 
>> >>> >> check.later(func() { 
>> >>> >> if !Comparable(typ.key) { 
>> >>> >> check.errorf(e.Key.Pos(), "invalid map key type 
>> %s", typ.key) 
>> >>> >> } 
>> >>> >> }) 
>> >>> >> // Comparable reports whether values of type T are comparable. 
>> >>> >> func Comparable(T Type) bool { 
>> >>> >> switch t := T.Underlying().(type) { 
>> >>> >> case *Basic: 
>> >>> >> // assume invalid types to be comparable 
>> >>> >> // to avoid follow-up errors 
>> >>> >> return t.kind != UntypedNil 
>> >>> >> case *Pointer, *Interface, *Chan: 
>> >>> >> return true 
>> >>> >> case *Struct: 
>> >>> >> for _, f := range t.fields { 
>> >>> >> if !Comparable(f.typ) { 
>> >>> >> return false 
>> >>> >> } 
>> >>> >> } 
>> >>> >> return true 
>> >>> >> case *Array: 
>> >>> >> return Comparable(t.elem) 
>> >>> >> } 
>> >>> >> return false 
>> >>> >> } 
>> >>> > 
>> >>> > -- 
>> >>> > 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 golang-nuts...@googlegroups.com. 
>> >>> > For more options, visit https://groups.google.com/d/optout. 
>> > 
>> > -- 
>> > You received this message because you are subscribed to the Google 
>> Groups "golang-nuts" group. 
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>> an email to golang-nuts...@googlegroups.com. 
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>>
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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-26 Thread mountainfpf 
I use it often, I don't know what you mean by this.

在 2019年1月25日星期五 UTC+8下午11:04:08，Burak Serdar写道：
>
> On Fri, Jan 25, 2019 at 7:47 AM Victor Giordano  > wrote: 
> > 
> > Just wanna say : It would be nice to employ a custom type as a valid key 
> for a map!!! :D 
>
> You can use a struct as a key. 
>
> > 
> > 
> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com 
> escribió: 
> >> 
> >> thanks lan. 
> >> 
> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道： 
> >>> 
> >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote: 
> >>> > 
> >>> > i got : 
> >>> >   # command-line-arguments 
> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be 
> compared to nil) 
> >>> 
> >>> Yes, that is what the language spec says and it is what I said: in Go, 
> >>> function values are not comparable. 
> >>> 
> >>> I wrote that code as an example to help explain why function values 
> >>> are not comparable. 
> >>> 
> >>> Ian 
> >>> 
> >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道： 
> >>> >> 
> >>> >>  When i use the func, map slice as the key of map, it isn't 
> work! 
> >>> >>  So  I lookup source  why, i find 
> >>> >> 
> >>> >> // spec: "The comparison operators == and != must be fully 
> defined 
> >>> >> // for operands of the key type; thus the key type must not 
> be a 
> >>> >> // function, map, or slice." 
> >>> >> // 
> >>> >> // Delay this check because it requires fully setup types; 
> >>> >> // it is safe to continue in any case (was issue 6667). 
> >>> >> check.later(func() { 
> >>> >> if !Comparable(typ.key) { 
> >>> >> check.errorf(e.Key.Pos(), "invalid map key type 
> %s", typ.key) 
> >>> >> } 
> >>> >> }) 
> >>> >> // Comparable reports whether values of type T are comparable. 
> >>> >> func Comparable(T Type) bool { 
> >>> >> switch t := T.Underlying().(type) { 
> >>> >> case *Basic: 
> >>> >> // assume invalid types to be comparable 
> >>> >> // to avoid follow-up errors 
> >>> >> return t.kind != UntypedNil 
> >>> >> case *Pointer, *Interface, *Chan: 
> >>> >> return true 
> >>> >> case *Struct: 
> >>> >> for _, f := range t.fields { 
> >>> >> if !Comparable(f.typ) { 
> >>> >> return false 
> >>> >> } 
> >>> >> } 
> >>> >> return true 
> >>> >> case *Array: 
> >>> >> return Comparable(t.elem) 
> >>> >> } 
> >>> >> return false 
> >>> >> } 
> >>> > 
> >>> > -- 
> >>> > 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 golang-nuts...@googlegroups.com. 
> >>> > For more options, visit https://groups.google.com/d/optout. 
> > 
> > -- 
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> Groups "golang-nuts" group. 
> > To unsubscribe from this group and stop receiving emails from it, send 
> an email to golang-nuts...@googlegroups.com . 
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>

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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-25 Thread Victor Giordano 
Yeah, i got the idea. I had already researched about it and what you can do 
about it. 

I was only repeating what i want as a dev in this community! 

El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel escribió:
>
> you can "employ" any custom type as key but the ones that doesn't 
> defines equality operations, see 
> https://golang.org/ref/spec#Comparison_operators 
> as Ian already pointed out, you just can't build your custom type on 
> top of func, map or slice to be a valid key, anything else you can. 
>
> On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano  > wrote: 
> > 
> > Just wanna say : It would be nice to employ a custom type as a valid key 
> for a map!!! :D 
> > 
> > 
> > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com 
> escribió: 
> >> 
> >> thanks lan. 
> >> 
> >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道： 
> >>> 
> >>> On Tue, Jan 22, 2019 at 11:47 PM  wrote: 
> >>> > 
> >>> > i got : 
> >>> >   # command-line-arguments 
> >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be 
> compared to nil) 
> >>> 
> >>> Yes, that is what the language spec says and it is what I said: in Go, 
> >>> function values are not comparable. 
> >>> 
> >>> I wrote that code as an example to help explain why function values 
> >>> are not comparable. 
> >>> 
> >>> Ian 
> >>> 
> >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道： 
> >>> >> 
> >>> >>  When i use the func, map slice as the key of map, it isn't 
> work! 
> >>> >>  So  I lookup source  why, i find 
> >>> >> 
> >>> >> // spec: "The comparison operators == and != must be fully 
> defined 
> >>> >> // for operands of the key type; thus the key type must not 
> be a 
> >>> >> // function, map, or slice." 
> >>> >> // 
> >>> >> // Delay this check because it requires fully setup types; 
> >>> >> // it is safe to continue in any case (was issue 6667). 
> >>> >> check.later(func() { 
> >>> >> if !Comparable(typ.key) { 
> >>> >> check.errorf(e.Key.Pos(), "invalid map key type 
> %s", typ.key) 
> >>> >> } 
> >>> >> }) 
> >>> >> // Comparable reports whether values of type T are comparable. 
> >>> >> func Comparable(T Type) bool { 
> >>> >> switch t := T.Underlying().(type) { 
> >>> >> case *Basic: 
> >>> >> // assume invalid types to be comparable 
> >>> >> // to avoid follow-up errors 
> >>> >> return t.kind != UntypedNil 
> >>> >> case *Pointer, *Interface, *Chan: 
> >>> >> return true 
> >>> >> case *Struct: 
> >>> >> for _, f := range t.fields { 
> >>> >> if !Comparable(f.typ) { 
> >>> >> return false 
> >>> >> } 
> >>> >> } 
> >>> >> return true 
> >>> >> case *Array: 
> >>> >> return Comparable(t.elem) 
> >>> >> } 
> >>> >> return false 
> >>> >> } 
> >>> > 
> >>> > -- 
> >>> > 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 golang-nuts...@googlegroups.com. 
> >>> > For more options, visit https://groups.google.com/d/optout. 
> > 
> > -- 
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> Groups "golang-nuts" group. 
> > To unsubscribe from this group and stop receiving emails from it, send 
> an email to golang-nuts...@googlegroups.com . 
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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-25 Thread Wagner Riffel 
you can "employ" any custom type as key but the ones that doesn't
defines equality operations, see
https://golang.org/ref/spec#Comparison_operators
as Ian already pointed out, you just can't build your custom type on
top of func, map or slice to be a valid key, anything else you can.

On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano  wrote:
>
> Just wanna say : It would be nice to employ a custom type as a valid key for 
> a map!!! :D
>
>
> El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com escribió:
>>
>> thanks lan.
>>
>> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
>>>
>>> On Tue, Jan 22, 2019 at 11:47 PM  wrote:
>>> >
>>> > i got :
>>> >   # command-line-arguments
>>> > ./key.go:6:18: invalid operation: F() == F() (func can only be compared 
>>> > to nil)
>>>
>>> Yes, that is what the language spec says and it is what I said: in Go,
>>> function values are not comparable.
>>>
>>> I wrote that code as an example to help explain why function values
>>> are not comparable.
>>>
>>> Ian
>>>
>>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
>>> >>
>>> >>  When i use the func, map slice as the key of map, it isn't work!
>>> >>  So  I lookup source  why, i find
>>> >>
>>> >> // spec: "The comparison operators == and != must be fully defined
>>> >> // for operands of the key type; thus the key type must not be a
>>> >> // function, map, or slice."
>>> >> //
>>> >> // Delay this check because it requires fully setup types;
>>> >> // it is safe to continue in any case (was issue 6667).
>>> >> check.later(func() {
>>> >> if !Comparable(typ.key) {
>>> >> check.errorf(e.Key.Pos(), "invalid map key type %s", 
>>> >> typ.key)
>>> >> }
>>> >> })
>>> >> // Comparable reports whether values of type T are comparable.
>>> >> func Comparable(T Type) bool {
>>> >> switch t := T.Underlying().(type) {
>>> >> case *Basic:
>>> >> // assume invalid types to be comparable
>>> >> // to avoid follow-up errors
>>> >> return t.kind != UntypedNil
>>> >> case *Pointer, *Interface, *Chan:
>>> >> return true
>>> >> case *Struct:
>>> >> for _, f := range t.fields {
>>> >> if !Comparable(f.typ) {
>>> >> return false
>>> >> }
>>> >> }
>>> >> return true
>>> >> case *Array:
>>> >> return Comparable(t.elem)
>>> >> }
>>> >> return false
>>> >> }
>>> >
>>> > --
>>> > 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 golang-nuts...@googlegroups.com.
>>> > For more options, visit https://groups.google.com/d/optout.
>
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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-25 Thread Burak Serdar 
On Fri, Jan 25, 2019 at 7:47 AM Victor Giordano  wrote:
>
> Just wanna say : It would be nice to employ a custom type as a valid key for 
> a map!!! :D

You can use a struct as a key.

>
>
> El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com escribió:
>>
>> thanks lan.
>>
>> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
>>>
>>> On Tue, Jan 22, 2019 at 11:47 PM  wrote:
>>> >
>>> > i got :
>>> >   # command-line-arguments
>>> > ./key.go:6:18: invalid operation: F() == F() (func can only be compared 
>>> > to nil)
>>>
>>> Yes, that is what the language spec says and it is what I said: in Go,
>>> function values are not comparable.
>>>
>>> I wrote that code as an example to help explain why function values
>>> are not comparable.
>>>
>>> Ian
>>>
>>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
>>> >>
>>> >>  When i use the func, map slice as the key of map, it isn't work!
>>> >>  So  I lookup source  why, i find
>>> >>
>>> >> // spec: "The comparison operators == and != must be fully defined
>>> >> // for operands of the key type; thus the key type must not be a
>>> >> // function, map, or slice."
>>> >> //
>>> >> // Delay this check because it requires fully setup types;
>>> >> // it is safe to continue in any case (was issue 6667).
>>> >> check.later(func() {
>>> >> if !Comparable(typ.key) {
>>> >> check.errorf(e.Key.Pos(), "invalid map key type %s", 
>>> >> typ.key)
>>> >> }
>>> >> })
>>> >> // Comparable reports whether values of type T are comparable.
>>> >> func Comparable(T Type) bool {
>>> >> switch t := T.Underlying().(type) {
>>> >> case *Basic:
>>> >> // assume invalid types to be comparable
>>> >> // to avoid follow-up errors
>>> >> return t.kind != UntypedNil
>>> >> case *Pointer, *Interface, *Chan:
>>> >> return true
>>> >> case *Struct:
>>> >> for _, f := range t.fields {
>>> >> if !Comparable(f.typ) {
>>> >> return false
>>> >> }
>>> >> }
>>> >> return true
>>> >> case *Array:
>>> >> return Comparable(t.elem)
>>> >> }
>>> >> return false
>>> >> }
>>> >
>>> > --
>>> > 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 golang-nuts...@googlegroups.com.
>>> > For more options, visit https://groups.google.com/d/optout.
>
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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-25 Thread Victor Giordano 
Just wanna say : It would be nice to employ a custom type as a valid key 
for a map!!! :D


El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com 
escribió:
>
> thanks lan.
>
> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
>>
>> On Tue, Jan 22, 2019 at 11:47 PM  wrote: 
>> > 
>> > i got : 
>> >   # command-line-arguments 
>> > ./key.go:6:18: invalid operation: F() == F() (func can only be compared 
>> to nil) 
>>
>> Yes, that is what the language spec says and it is what I said: in Go, 
>> function values are not comparable. 
>>
>> I wrote that code as an example to help explain why function values 
>> are not comparable. 
>>
>> Ian 
>>
>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道： 
>> >> 
>> >>  When i use the func, map slice as the key of map, it isn't work! 
>> >>  So  I lookup source  why, i find 
>> >> 
>> >> // spec: "The comparison operators == and != must be fully defined 
>> >> // for operands of the key type; thus the key type must not be 
>> a 
>> >> // function, map, or slice." 
>> >> // 
>> >> // Delay this check because it requires fully setup types; 
>> >> // it is safe to continue in any case (was issue 6667). 
>> >> check.later(func() { 
>> >> if !Comparable(typ.key) { 
>> >> check.errorf(e.Key.Pos(), "invalid map key type %s", 
>> typ.key) 
>> >> } 
>> >> }) 
>> >> // Comparable reports whether values of type T are comparable. 
>> >> func Comparable(T Type) bool { 
>> >> switch t := T.Underlying().(type) { 
>> >> case *Basic: 
>> >> // assume invalid types to be comparable 
>> >> // to avoid follow-up errors 
>> >> return t.kind != UntypedNil 
>> >> case *Pointer, *Interface, *Chan: 
>> >> return true 
>> >> case *Struct: 
>> >> for _, f := range t.fields { 
>> >> if !Comparable(f.typ) { 
>> >> return false 
>> >> } 
>> >> } 
>> >> return true 
>> >> case *Array: 
>> >> return Comparable(t.elem) 
>> >> } 
>> >> return false 
>> >> } 
>> > 
>> > -- 
>> > 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 golang-nuts...@googlegroups.com. 
>> > For more options, visit https://groups.google.com/d/optout. 
>>
>

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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-23 Thread mountainfpf 
thanks lan.

在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道：
>
> On Tue, Jan 22, 2019 at 11:47 PM > 
> wrote: 
> > 
> > i got : 
> >   # command-line-arguments 
> > ./key.go:6:18: invalid operation: F() == F() (func can only be compared 
> to nil) 
>
> Yes, that is what the language spec says and it is what I said: in Go, 
> function values are not comparable. 
>
> I wrote that code as an example to help explain why function values 
> are not comparable. 
>
> Ian 
>
> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道： 
> >> 
> >>  When i use the func, map slice as the key of map, it isn't work! 
> >>  So  I lookup source  why, i find 
> >> 
> >> // spec: "The comparison operators == and != must be fully defined 
> >> // for operands of the key type; thus the key type must not be 
> a 
> >> // function, map, or slice." 
> >> // 
> >> // Delay this check because it requires fully setup types; 
> >> // it is safe to continue in any case (was issue 6667). 
> >> check.later(func() { 
> >> if !Comparable(typ.key) { 
> >> check.errorf(e.Key.Pos(), "invalid map key type %s", 
> typ.key) 
> >> } 
> >> }) 
> >> // Comparable reports whether values of type T are comparable. 
> >> func Comparable(T Type) bool { 
> >> switch t := T.Underlying().(type) { 
> >> case *Basic: 
> >> // assume invalid types to be comparable 
> >> // to avoid follow-up errors 
> >> return t.kind != UntypedNil 
> >> case *Pointer, *Interface, *Chan: 
> >> return true 
> >> case *Struct: 
> >> for _, f := range t.fields { 
> >> if !Comparable(f.typ) { 
> >> return false 
> >> } 
> >> } 
> >> return true 
> >> case *Array: 
> >> return Comparable(t.elem) 
> >> } 
> >> return false 
> >> } 
> > 
> > -- 
> > 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 golang-nuts...@googlegroups.com . 
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Re: [go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-23 Thread Ian Lance Taylor 
On Tue, Jan 22, 2019 at 11:47 PM  wrote:
>
> i got :
>   # command-line-arguments
> ./key.go:6:18: invalid operation: F() == F() (func can only be compared to 
> nil)

Yes, that is what the language spec says and it is what I said: in Go,
function values are not comparable.

I wrote that code as an example to help explain why function values
are not comparable.

Ian

> 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
>>
>>  When i use the func, map slice as the key of map, it isn't work!
>>  So  I lookup source  why, i find
>>
>> // spec: "The comparison operators == and != must be fully defined
>> // for operands of the key type; thus the key type must not be a
>> // function, map, or slice."
>> //
>> // Delay this check because it requires fully setup types;
>> // it is safe to continue in any case (was issue 6667).
>> check.later(func() {
>> if !Comparable(typ.key) {
>> check.errorf(e.Key.Pos(), "invalid map key type %s", typ.key)
>> }
>> })
>> // Comparable reports whether values of type T are comparable.
>> func Comparable(T Type) bool {
>> switch t := T.Underlying().(type) {
>> case *Basic:
>> // assume invalid types to be comparable
>> // to avoid follow-up errors
>> return t.kind != UntypedNil
>> case *Pointer, *Interface, *Chan:
>> return true
>> case *Struct:
>> for _, f := range t.fields {
>> if !Comparable(f.typ) {
>> return false
>> }
>> }
>> return true
>> case *Array:
>> return Comparable(t.elem)
>> }
>> return false
>> }
>
> --
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[go-nuts] Re: why map the key type must not be a function, map, or slice

2019-01-22 Thread mountainfpf 
exec code:
package main

import "fmt"

func main() {
fmt.Println(F() == F())
}

func F() func() int {
i := 0
return func() int {
i++
return i
}
}


i got :
  # command-line-arguments
./key.go:6:18: invalid operation: F() == F() (func can only be compared to 
nil)


在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道：
>
>  When i use the func, map slice as the key of map, it isn't work! 
>  So  I lookup source  why, i find 
>
> // spec: "The comparison operators == and != must be fully defined
> // for operands of the key type; thus the key type must not be a
> // function, map, or slice."
> //
> // Delay this check because it requires fully setup types;
> // it is safe to continue in any case (was issue 6667).
> check.later(func() {
> if !Comparable(typ.key) {
> check.errorf(e.Key.Pos(), "invalid map key type %s", 
> typ.key)
> }
> })
> // Comparable reports whether values of type T are comparable.
> func Comparable(T Type) bool {
> switch t := T.Underlying().(type) {
> case *Basic:
> // assume invalid types to be comparable
> // to avoid follow-up errors
> return t.kind != UntypedNil
> case *Pointer, *Interface, *Chan:
> return true
> case *Struct:
> for _, f := range t.fields {
> if !Comparable(f.typ) {
> return false
> }
> }
> return true
> case *Array:
> return Comparable(t.elem)
> }
> return false
> }
>

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