Numbering a,b-variants of assumptions (or other theorem-like environments) without using `amsthm`

Question

I would like to have variants of assumptions (sub-assumptions, if you like) labeled and referenced as 1a, 2b, etc., without using the amsthm package which is known to conflict with the publisher's house style (INFORMS Management Science style file). MWE:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Author template for Management Science (mnsc) for articles with no e-companion (EC)
%% Mirko Janc, Ph.D., INFORMS, [email protected]
%% ver. 0.95, December 2010
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[mnsc,blindrev]{informs3}
%\documentclass[mnsc,nonblindrev]{informs3} % current default for manuscript submission

\OneAndAHalfSpacedXI
%%\OneAndAHalfSpacedXII % Current default line spacing
%%\DoubleSpacedXII
%%\DoubleSpacedXI

% If hyperref is used, dvi-to-ps driver of choice must be declared as
%   an additional option to the \documentclass. For example
%\documentclass[dvips,mnsc]{informs3}      % if dvips is used
%\documentclass[dvipsone,mnsc]{informs3}   % if dvipsone is used, etc.

% Private macros here (check that there is no clash with the style)


%% Setup of theorem styles. Outcomment only one.
%% Preferred default is the first option.
\TheoremsNumberedThrough     % Preferred (Theorem 1, Lemma 1, Theorem 2)
%\TheoremsNumberedByChapter  % (Theorem 1.1, Lema 1.1, Theorem 1.2)
\ECRepeatTheorems

%% Setup of the equation numbering system. Outcomment only one.
%% Preferred default is the first option.
\EquationsNumberedThrough    % Default: (1), (2), ...
%\EquationsNumberedBySection % (1.1), (1.2), ...

% For new submissions, leave this number blank.
% For revisions, input the manuscript number assigned by the on-line
% system along with a suffix ".Rx" where x is the revision number.
\MANUSCRIPTNO{MS-0001-1922.65}

%%%%%%%%%%%%%%%%
\begin{document}
%%%%%%%%%%%%%%%%

\begin{assumption}
    The first assumption.
\end{assumption}

Some text\ldots

\begin{assumption}
    I want this to be displayed and referenced as ``Assumption~2a''.
\end{assumption}

Some text\ldots (If the text here interferes with the solution, it can be omitted.)

\begin{assumption}
    I want this to be displayed and referenced as ``Assumption~2b''.
\end{assumption}

Some text\ldots

\begin{assumption}
    I want this to be displayed and referenced as ``Assumption~3''.
\end{assumption}

%%%%%%%%%%%%%%%%%
\end{document}
%%%%%%%%%%%%%%%%%

The answer to a related question uses the amsthm package. I also tried the answer here but it didn't work either.

*Probably unrelated to the solution: Eventually I would also like to add a prime(') to some of the assumption variants (e.g., Assumption~2b') with this method; so I hope the solution is compatible with it as well.

Answer 1

Some fighting against small caps, but for the rest quite straightforward.

If you need different consecutive groups of subassumptions, you can just issue \stepcounter{assumption} between the groups.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Author template for Management Science (mnsc) for articles with no e-companion (EC)
%% Mirko Janc, Ph.D., INFORMS, [email protected]
%% ver. 0.95, December 2010
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[mnsc,blindrev]{informs3}
%\documentclass[mnsc,nonblindrev]{informs3} % current default for manuscript submission

\OneAndAHalfSpacedXI
%%\OneAndAHalfSpacedXII % Current default line spacing
%%\DoubleSpacedXII
%%\DoubleSpacedXI

% If hyperref is used, dvi-to-ps driver of choice must be declared as
%   an additional option to the \documentclass. For example
%\documentclass[dvips,mnsc]{informs3}      % if dvips is used
%\documentclass[dvipsone,mnsc]{informs3}   % if dvipsone is used, etc.

% Private macros here (check that there is no clash with the style)


%% Setup of theorem styles. Outcomment only one.
%% Preferred default is the first option.
\TheoremsNumberedThrough     % Preferred (Theorem 1, Lemma 1, Theorem 2)
%\TheoremsNumberedByChapter  % (Theorem 1.1, Lema 1.1, Theorem 1.2)
\ECRepeatTheorems

%% Setup of the equation numbering system. Outcomment only one.
%% Preferred default is the first option.
\EquationsNumberedThrough    % Default: (1), (2), ...
%\EquationsNumberedBySection % (1.1), (1.2), ...

% For new submissions, leave this number blank.
% For revisions, input the manuscript number assigned by the on-line
% system along with a suffix ".Rx" where x is the revision number.
\MANUSCRIPTNO{MS-0001-1922.65}

\newtheorem{subassumption}{Assumption\normalfont}[assumption]
\renewcommand{\thesubassumption}{\theassumption\alph{subassumption}}}

\newenvironment{assumption*}
 {\ifnum\value{subassumption}=0 \stepcounter{assumption}\fi\subassumption}
 {\endsubassumption}
\newenvironment{assumption+}[1]
 {\renewcommand{\thesubassumption}{#1}\subassumption}
 {\endsubassumption}

%%%%%%%%%%%%%%%%
\begin{document}
%%%%%%%%%%%%%%%%

\begin{assumption}\label{a1}
    The first assumption.
\end{assumption}

Some text\ldots

\begin{assumption*}\label{a2a}
    I want this to be displayed and referenced as ``Assumption~2a''.
\end{assumption*}

Some text\ldots (If the text here interferes with the solution, it can be omitted.)

\begin{assumption*}\label{a2b}
    I want this to be displayed and referenced as ``Assumption~2b''.
\end{assumption*}

Some text\ldots

\begin{assumption+}{\ref{a2b}$'$}\label{a2b'}
    I want this to be displayed and referenced as ``Assumption~2b''.
\end{assumption+}

Some text\ldots

\begin{assumption}\label{a3}
    I want this to be displayed and referenced as ``Assumption~3''.
\end{assumption}

References: \ref{a1}, \ref{a2a}, \ref{a2b}, \ref{a2b'}, \ref{a3}.

%%%%%%%%%%%%%%%%%
\end{document}
%%%%%%%%%%%%%%%%%

Different version, introducing a subassumptions environment, modeled on subequations.

I define the auxiliary environment fixedassumption in order to avoid the label 2a printed in small caps.

Note that in this version assumption* is used instead of assumption+ of the previous version.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Author template for Management Science (mnsc) for articles with no e-companion (EC)
%% Mirko Janc, Ph.D., INFORMS, [email protected]
%% ver. 0.95, December 2010
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[mnsc,blindrev]{informs3}
%\documentclass[mnsc,nonblindrev]{informs3} % current default for manuscript submission

\OneAndAHalfSpacedXI
%%\OneAndAHalfSpacedXII % Current default line spacing
%%\DoubleSpacedXII
%%\DoubleSpacedXI

% If hyperref is used, dvi-to-ps driver of choice must be declared as
%   an additional option to the \documentclass. For example
%\documentclass[dvips,mnsc]{informs3}      % if dvips is used
%\documentclass[dvipsone,mnsc]{informs3}   % if dvipsone is used, etc.

% Private macros here (check that there is no clash with the style)


%% Setup of theorem styles. Outcomment only one.
%% Preferred default is the first option.
\TheoremsNumberedThrough     % Preferred (Theorem 1, Lemma 1, Theorem 2)
%\TheoremsNumberedByChapter  % (Theorem 1.1, Lema 1.1, Theorem 1.2)
\ECRepeatTheorems

%% Setup of the equation numbering system. Outcomment only one.
%% Preferred default is the first option.
\EquationsNumberedThrough    % Default: (1), (2), ...
%\EquationsNumberedBySection % (1.1), (1.2), ...

% For new submissions, leave this number blank.
% For revisions, input the manuscript number assigned by the on-line
% system along with a suffix ".Rx" where x is the revision number.
\MANUSCRIPTNO{MS-0001-1922.65}

% not to be used directly
\newcounter{subassumption}
\theoremstyle{TH}
\newtheorem{fixedassumption}[assumption]{Assumption\normalfont}
\newenvironment{subassumptions}
 {%
  \refstepcounter{assumption}%
  \edef\theassumption{\theassumption\noexpand\alph{assumption}}%
  \setcounter{subassumption}{\value{assumption}}%
  \setcounter{assumption}{0}%
  \let\assumption\fixedassumption
  \let\endassumption\endfixedassumption
  \ignorespaces
 }
 {\setcounter{assumption}{\value{subassumption}}\ignorespacesafterend}

\newenvironment{assumption*}[1]
 {\renewcommand{\theassumption}{#1}\fixedassumption}
 {\endfixedassumption}

%%%%%%%%%%%%%%%%
\begin{document}
%%%%%%%%%%%%%%%%

\begin{assumption}\label{a1}
    The first assumption.
\end{assumption}

Some text\ldots

\begin{subassumptions}
\begin{assumption}\label{a2a}
    I want this to be displayed and referenced as ``Assumption~2a''.
\end{assumption}

Some text\ldots (If the text here interferes with the solution, it can be omitted.)

\begin{assumption}\label{a2b}
    I want this to be displayed and referenced as ``Assumption~2b''.
\end{assumption}
\end{subassumptions}

Some text\ldots

\begin{assumption*}{\ref{a2b}$'$}\label{a2b'}
    I want this to be displayed and referenced as ``Assumption~2b''.
\end{assumption*}

Some text\ldots

\begin{assumption}\label{a3}
    I want this to be displayed and referenced as ``Assumption~3''.
\end{assumption}

References: \ref{a1}, \ref{a2a}, \ref{a2b}, \ref{a2b'}, \ref{a3}.

%%%%%%%%%%%%%%%%%
\end{document}
%%%%%%%%%%%%%%%%%

Answer 2

Perhaps I misunderstand the question, it seems that this requires two different environments: one for assumptions and one for subassumptions. Under the hood, all of the theorem-like environments use \trivlist so the natural thing to do here is to define new environments that use the same mechanism.

The code below defines two environments, assumption and assumption*, for assumptions and subassumptions. As with the standard theorem-like environments, both of these environments accept an optional argument. Adapting the MWE above, the output is:

Here is the code:

\documentclass{article}

\newcounter{assumption}
\newcounter{subassumption}
\renewcommand\theassumption{Assumption~\arabic{assumption}}
\renewcommand\thesubassumption{\theassumption\alph{subassumption}}
\makeatletter
\@addtoreset{subassumption}{assumption}
\newenvironment{assumption}[1][]{%
  \refstepcounter{assumption}%
  \def\@currentlabel{Assumption~\arabic{assumption}}%
  \if\relax\detokenize{#1}\relax\let\@assumptionextra\relax%
  \else\def\@assumptionextra{\space(#1)}%
  \fi%
  \trivlist\item[\textsc{Assumption}~\arabic{assumption}\@assumptionextra\space]%
    \ignorespaces\itshape%
  }{\endtrivlist}%
\newenvironment{assumption*}[1][]{%
  % change the assumption counter if this is the first subassumption
  \ifnum\value{subassumption}=0\refstepcounter{assumption}\fi%
  \refstepcounter{subassumption}%
  \def\@currentlabel{Assumption~\arabic{assumption}\alph{subassumption}}%
  \if\relax\detokenize{#1}\relax\let\@assumptionextra\relax%
  \else\def\@assumptionextra{\space(#1)}%
  \fi%
  \trivlist\item[\textsc{Assumption}~\arabic{assumption}\alph{subassumption}%
    \@assumptionextra\space]\ignorespaces\itshape%
  }{\endtrivlist}%
\makeatother

\begin{document}

    \begin{assumption}
        The first assumption.
        \label{Assumption1}
    \end{assumption}

    Some text\ldots

    \begin{assumption*}
        I want this to be displayed and referenced as ``Assumption~2a''.
        \label{Assumption2a}
    \end{assumption*}

    Some text\ldots (If the text here interferes with the solution, it can be omitted.)

    \begin{assumption*}
        I want this to be displayed and referenced as ``Assumption~2b''.
        \label{Assumption2b}
    \end{assumption*}

    \begin{assumption*}[$c>a$]
        I want this to be displayed and referenced as ``Assumption~2b''.
        \label{Assumption2c}
    \end{assumption*}

    Some text\ldots

    \begin{assumption}
        I want this to be displayed and referenced as ``Assumption~3''.
        \label{Assumption3}
    \end{assumption}

    Labels: \ref{Assumption1}, \ref{Assumption2a}, \ref{Assumption2b}
    and \ref{Assumption3}

\end{document}