How can I align two boxes to the top right and top left of a surrounding box?

Question

Assuming the following structure (auto-generated from another document), how should I define \csup and \csub to line the sup boxes to line up with the top of the neighbouring box, and the sub boxes to line up with the bottom?

\documentclass{article}
\newcommand*{\csup}[1]{\scriptsize{#1}}
\newcommand*{\csub}[1]{\scriptsize{#1}}
\newcommand*{\cnotation}[1]{#1}
\newcommand*{\crepeat}[1]{\fbox{#1}}
\newcommand*{\cwrapper}[1]{#1}

\begin{document}
\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper{\crepeat{CCC}\csup{pC}\csub{bC}}}
      \csup{pB}\csub{bB}}}
  \csup{pA}\csub{bA}}
\end{document}

In other words, how do I change the document to produce this:

instead of this?

I tried raisebox and adjustbox, but the following is the best I could get:

\newcommand*{\csup}[1]{\adjustbox{valign=t}{\scriptsize{\rlap{#1}}}}
\newcommand*{\csub}[1]{\adjustbox{valign=b}{\scriptsize{#1}}}

Answer 1

(simplified the answer to show both candidate solution methods in one go)

Here are two candidate solutions. The first positions the sub- and superscript terms relative to the right-hand edge of the immediately preceding box, while the second ignores the height of the immediately preceding box.

The main changes, relative to your code, are (a) making \cwrapper take three arguments (#1: the material to be placed in a box; #2 and #3: the superscript and subscript terms) and (b) using math mode to help position the super- and subscript terms relative to the preceding material.

\documentclass{article}
\newcommand*{\cscr}[1]{\textnormal{\scriptsize #1}}
\newcommand*{\cwrappera}[3]{%
    $\left.{\textnormal{\fbox{#1}}}\ \right.^{\cscr{#2}}_{\cscr{#3}}$}
\newcommand*{\cwrapperb}[3]{%
    \fbox{#1} ${\vphantom{\textnormal{#1}}}^{\cscr{#2}}_{\cscr{#3}}$}

\begin{document}
\cwrappera{AAA
    \cwrappera{BBB
        \cwrappera{CCC}{pC}{bC}}
        {pB}{bB}}
    {pA}{bA} 

\medskip
\cwrapperb{AAA
    \cwrapperb{BBB
        \cwrapperb{CCC}{pC}{bC}}
        {pB}{bB}}
    {pA}{bA}        
\end{document}

Answer 2

The original syntax of the OP can be preserved with this formulation:

\documentclass{article}
\usepackage{amsmath}
\newcommand*{\csub}[1]{_\textnormal{~#1}}
\newcommand*{\csup}[1]{^\textnormal{~#1}}
\newcommand*{\cnotation}[1]{#1}
\newcommand*{\crepeat}[1]{\fbox{#1}}
\newcommand*{\cwrapper}[1]{\ensuremath{#1}}
\begin{document}
\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper{\crepeat{CCC}\csup{pC}\csub{bC}}}
      \csup{pB}\csub{bB}}}
  \csup{pA}\csub{bA}}
\end{document}

I use \cwrapper to ensure math mode, and then use \csub and \csup to employ math sub and superscripts with \text macros.

---

If one wants the sub- and superscripts tighter, then this would do, where I have moved the subscript up 1pt and the superscript down 2.5pt:

\documentclass{article}
\usepackage{amsmath}
\newcommand*{\csub}[1]{_\textnormal{~#1}}
\newcommand*{\csup}[1]{^\textnormal{~#1}}
\newcommand*{\cnotation}[1]{#1}
\newcommand*{\crepeat}[1]{\setbox0=\hbox{\fbox{#1}}\ht0=\dimexpr\ht0-2.5pt\relax%
  \dp0=\dimexpr\dp0-1pt\relax\box0}
\newcommand*{\cwrapper}[1]{\ensuremath{#1}}
\begin{document}
\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper{\crepeat{CCC}\csup{pC}\csub{bC}}}
      \csup{pB}\csub{bB}}}
  \csup{pA}\csub{bA}}
\end{document}

Answer 3

Here's a version respecting the clumsy syntax you want.

\documentclass{article}

\makeatletter
\newcommand{\cwrapper}[1]{%
  \leavevmode\check@mathfonts
  \begingroup\ignorespaces
  #1%
  \clement@wrap
  \endgroup
}
\newcommand{\crepeat}[1]{%
  \def\clement@repeat{#1}\ignorespaces
}
\newcommand{\csup}[1]{\def\clement@sup{#1}\ignorespaces}
\newcommand{\csub}[1]{\def\clement@sub{#1}\ignorespaces}
\newcommand{\clement@wrap}{%
  \sbox\z@{\fbox{\clement@repeat}}%
  \copy\z@
  \raisebox{-\dp\z@}{%
    \vbox to \dimexpr\ht\z@+\dp\z@{
      \hrule height\z@
      \hbox{\fontsize\sf@size\z@\selectfont\clement@sup}
      \vss
      \hbox{\fontsize\sf@size\z@\selectfont\clement@sub}
      \hrule height\z@
    }%
  }%
}
\makeatother

\begin{document}

\cwrapper{\crepeat{AAA}\csup{a}\csub{b}}

\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper{\crepeat{CCC}\csup{pC}\csub{bC}}}
      \csup{pB}\csub{bB}}}
  \csup{pA}\csub{bA}}

\Large
\cwrapper{\crepeat{AAA}\csup{a}\csub{b}}

\end{document}

Note that also font size changes are respected.

Answer 4

Just because it is there, here's a version which uses coffins to arrange and typeset the boxes.

The syntax is identical to that specified in the question except that \cwrapper can take an optional argument specifying the horizontal distance between the larger box and the superscript and subscripts. Since this is optional, the OP's syntax can be used unchanged. In that case, the default is 1pt, but this can obviously be modified as desired.

Essentially, each of \csup, \csub and \crepeat is defined to put its content into a coffin. \cwrapper is defined to join the coffins appropriately and typeset the result. Nesting works as expected, as shown in the extended example below.

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\coffin_new:N \l_clement_main_coffin
\coffin_new:N \l_clement_tmpa_coffin
\coffin_new:N \l_clement_sup_coffin
\coffin_new:N \l_clement_sub_coffin
\dim_new:N \l_clement_spacer_dim
\NewDocumentCommand \csup { m }
{
  \hcoffin_set:Nn \l_clement_sup_coffin { \scriptsize #1 }
}
\NewDocumentCommand \csub { m }
{
  \hcoffin_set:Nn \l_clement_sub_coffin { \scriptsize #1 }
}
\NewDocumentCommand \crepeat { m }
{
  \hcoffin_set:Nn \l_clement_tmpa_coffin { \fbox { \tl_trim_spaces:n { #1 } } }
}
\NewDocumentCommand \cwrapper { O { 1pt } m }
{
  \group_begin:
    \clement_cwrapper:nn { #1 } { #2 }
  \group_end:
}
\cs_generate_variant:Nn \coffin_join:NnnNnnnn { NnnNnnVn }
\cs_new_protected:Npn \clement_cwrapper:nn #1 #2
{
  #2
  \dim_set:Nn \l_clement_spacer_dim { #1 }
  \coffin_join:NnnNnnVn \l_clement_tmpa_coffin { r } { t } \l_clement_sup_coffin { l } { t } \l_clement_spacer_dim { 0pt }
  \coffin_join:NnnNnnVn \l_clement_tmpa_coffin { \l_clement_tmpa_coffin-r } { \l_clement_tmpa_coffin-b } \l_clement_sub_coffin { l } { b } \l_clement_spacer_dim { 0pt }
  \coffin_set_eq:NN \l_clement_main_coffin \l_clement_tmpa_coffin
  \coffin_typeset:Nnnnn \l_clement_main_coffin { l } { H } { 0pt } { 0pt }
}
\ExplSyntaxOff
\begin{document}
\cwrapper{\crepeat{%
    AAA
  }%
  \csup{pA}\csub{bA}%
}

\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
      }%
      \csup{pB}\csub{bB}%
    }%
  }%
  \csup{pA}\csub{bA}%
}

\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper{\crepeat{CCC}\csup{pC}\csub{bC}%
        }%
      }%
      \csup{pB}\csub{bB}%
    }%
  }%
  \csup{pA}\csub{bA}%
}

\cwrapper[5pt]{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper[10pt]{\crepeat{CCC}\csup{pC}\csub{bC}%
        }%
      }%
    }%
  }%
  \csup{pA}\csub{bA}%
}

\cwrapper{\crepeat{%
    AAA
    \cwrapper{\crepeat{%
        BBB
        \cwrapper{\crepeat{CCC}\csup{pC}%
        }%
      }%
      \csub{bB}%
    }%
  }%
}

\end{document}