#5694 Dot_configuration maintenance

[Dan Eble]

1: iterate properly in reverse
The previous code would have malfunctioned for an empty container.

2: swap instead of copy

3: reduce repetition using a lambda function

4: use range-for loops

5: Dot_configuration "has a" instead of "is a" std::map

It is considered poor form to create subclasses of standard containers
because they lack virtual destructors. Inheriting privately from
std::map avoids potential problems by preventing Dot_configuration from
being treated as a std::map from the outside. (I didn't find any actual
problems in this case.)

Limiting the Dot_configuration interface to just the map methods that
are actually used makes it easier to understand how Dot_configuration is
used without searching the entire code.

https://codereview.appspot.com/577380046

[Anonymous]

Passes make, make check and a full make doc.

[Anonymous]

Patch on countdown for Jan 29th

[Anonymous]

Patch counted down - please push

[Dan Eble]

commit cd83bbc1eb44224ab3c0268d78a862e3d9987988
Author: Dan Eble <nine.fierce.ballads@gmail.com>
Date:   Mon Nov 4 18:51:53 2019 -0500

    Issue 5694/5: Dot_configuration "has a" instead of "is a" std::map

    It is considered poor form to create subclasses of standard containers
    because they lack virtual destructors.  Inheriting privately from
    std::map avoids potential problems by preventing Dot_configuration from
    being treated as a std::map from the outside.  (I didn't find any actual
    problems in this case.)

    Limiting the Dot_configuration interface to just the map methods that
    are actually used makes it easier to understand how Dot_configuration is
    used without searching the entire code.

commit 2c7fbb3196f28246a389c8e96d6aa5fdd02b3938
Author: Dan Eble <nine.fierce.ballads@gmail.com>
Date:   Mon Nov 4 18:51:53 2019 -0500

    Issue 5694/4: Dot_configuration: use range-for loops

commit d720cf21b540e58c81c82c04584def0b254ef21e
Author: Dan Eble <nine.fierce.ballads@gmail.com>
Date:   Sat Jan 25 10:43:59 2020 -0500

    Issue 5694/3: Dot_configuration: reduce repetition using a lambda function

commit 1c3de1ef82563239979642194329e74669e3c62a
Author: Dan Eble <nine.fierce.ballads@gmail.com>
Date:   Mon Nov 4 18:51:53 2019 -0500

    Issue 5694/2: Dot_configuration: swap instead of copy

commit 15d5a6cf2cc6eb8621a9f06874684464defb6bf8
Author: Dan Eble <nine.fierce.ballads@gmail.com>
Date:   Sat Jan 25 10:42:37 2020 -0500

    Issue 5694/1: Dot_configuration: iterate properly in reverse

    The previous code would have malfunctioned for an empty container.