promise: include check into future body, i.e. joined results are always valid;
pending future derivations: shared ref within whole theory body, i.e. end-of-theory joins *all* derivations ever forked from a version of the theory;
simplified rep_deriv;
%% $Id$
\usepackage{ifthen}
\newcommand{\indexdef}[3]%
{\ifthenelse{\equal{}{#1}}{\index{#3 (#2)|bold}}{\index{#3 (#1\ #2)|bold}}}
\newcommand{\indexref}[3]{\ifthenelse{\equal{}{#1}}{\index{#3 (#2)}}{\index{#3 (#1\ #2)}}}
\newcommand{\isatt}[1]{{\def\isacharminus{-}\def\isacharunderscore{\_}\tt #1}}
\newcommand{\indexoutertoken}[1]{\indexdef{}{syntax}{#1}}
\newcommand{\indexouternonterm}[1]{\indexdef{}{syntax}{#1}}
\newcommand{\indexisarelem}[1]{\indexdef{}{element}{#1}}
\newcommand{\isasymAND}{\isakeyword{and}}
\newcommand{\isasymIS}{\isakeyword{is}}
\newcommand{\isasymWHERE}{\isakeyword{where}}
\newcommand{\isasymBEGIN}{\isakeyword{begin}}
\newcommand{\isasymIMPORTS}{\isakeyword{imports}}
\newcommand{\isasymIN}{\isakeyword{in}}
\newcommand{\isasymSTRUCTURE}{\isakeyword{structure}}
\newcommand{\isartrans}[2]{#1 \mathbin{\,\to\,} #2}
\newcommand{\isarkeep}[1]{#1 \mathbin{\,\to\,} #1}
\newcommand{\isarantiq}{antiquotation}
\newcommand{\isarmeth}{method}
\newcommand{\isaratt}{attribute}