How to use Multiway_Trees

How to use Multiway_Trees

[Mart van de Wege]

I was interested in using Ada.Containers.Multiway_Trees in another
project, so I wrote some Proof of Concept code to see if I understood
correctly how to use it.

However, even the most simple use case, the following code, raises a
Program_Error:

raised PROGRAM_ERROR : Tree_Test.Test_Tree.Replace_Element: Position cursor designates root

with Ada.Text_Io;
with Ada.Containers.Multiway_Trees;
procedure Test_Tree is
   type String_Access is access String;
   package Tr is new Ada.Containers.Multiway_Trees
     ( Element_Type => String_Access );
   use Tr;
   T : Tree := Empty_Tree;
   C : Cursor := Root(T);
begin
   T.Insert_Child(Parent => C,
                  Before => No_Element,
                  New_Item => new String'("Test"));
end Test_Tree;

How do I create a tree if I can't even insert a child under the root
node?

Mart

-- 
"We will need a longer wall when the revolution comes."
    --- AJS, quoting an uncertain source.

Re: How to use Multiway_Trees

[Niklas Holsti]

On 17-04-09 18:36 , Mart van de Wege wrote:
> I was interested in using Ada.Containers.Multiway_Trees in another
> project, so I wrote some Proof of Concept code to see if I understood
> correctly how to use it.
>
> However, even the most simple use case, the following code, raises a
> Program_Error:
>
> raised PROGRAM_ERROR : Tree_Test.Test_Tree.Replace_Element: Position cursor designates root
>
> with Ada.Text_Io;
> with Ada.Containers.Multiway_Trees;
> procedure Test_Tree is
>    type String_Access is access String;
>    package Tr is new Ada.Containers.Multiway_Trees
>      ( Element_Type => String_Access );
>    use Tr;
>    T : Tree := Empty_Tree;
>    C : Cursor := Root(T);
> begin
>    T.Insert_Child(Parent => C,
>                   Before => No_Element,
>                   New_Item => new String'("Test"));
> end Test_Tree;
>
> How do I create a tree if I can't even insert a child under the root
> node?
>
> Mart

That code works (no exceptions, and T.Node_Count = 2 after the 
Insert_Child) on my system, which is a Mac OS X 10.8.5 with GNAT GPL 
2012 (old, yes...).

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .

Re: How to use Multiway_Trees

[Simon Wright]

Niklas Holsti <niklas.holsti@tidorum.invalid> writes:

> That code works (no exceptions, and T.Node_Count = 2 after the
> Insert_Child) on my system, which is a Mac OS X 10.8.5 with GNAT GPL
> 2012 (old, yes...).

Also on macOS 10.12.4 with GNAT GPL 2016 and FSF GCC version 7.0.1 20170408

Re: How to use Multiway_Trees

[Mart van de Wege]

Simon Wright <simon@pushface.org> writes:

> Niklas Holsti <niklas.holsti@tidorum.invalid> writes:
>
>> That code works (no exceptions, and T.Node_Count = 2 after the
>> Insert_Child) on my system, which is a Mac OS X 10.8.5 with GNAT GPL
>> 2012 (old, yes...).
>
> Also on macOS 10.12.4 with GNAT GPL 2016 and FSF GCC version 7.0.1 20170408

Weird. This is a Debian Jessie system with gnat 6.1. Compilation is done
running straight gnatmake tree_test.adb.

Obviously I am doing something wrong; but what?

Mart

-- 
"We will need a longer wall when the revolution comes."
    --- AJS, quoting an uncertain source.

Re: How to use Multiway_Trees

[Dirk Heinrichs]

Am 09.04.2017 um 18:49 schrieb Mart van de Wege:

> This is a Debian Jessie system with gnat 6.1. Compilation is done
> running straight gnatmake tree_test.adb.

Works here, too. Debian Stretch with GCC version 6.3.0 20170321 (Debian
6.3.0-11).

Bye...

	Dirk
-- 
Dirk Heinrichs <dirk.heinrichs@altum.de>
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Re: How to use Multiway_Trees

[Mart van de Wege]

Dirk Heinrichs <dirk.heinrichs@altum.de> writes:

> Am 09.04.2017 um 18:49 schrieb Mart van de Wege:
>
>> This is a Debian Jessie system with gnat 6.1. Compilation is done
>> running straight gnatmake tree_test.adb.
>
> Works here, too. Debian Stretch with GCC version 6.3.0 20170321 (Debian
> 6.3.0-11).
>
Re-checked. I was wrong, this is not Jessie, but Sid, and the compiler
is gcc 6.3.0-4 (why does my Sid have an older version than your
Stretch?)

I think this is something to take to the Debian-Ada mailing list.

Mart

-- 
"We will need a longer wall when the revolution comes."
    --- AJS, quoting an uncertain source.