Restore the index marker, define a command for it

Author: eernstg

specification/dart.sty

@@ -173,9 +173,12 @@
 \newcommand{\id}{\metavar{id}}
 \newcommand{\op}{\metavar{op}}
 
+% Used in margin to indicate that a term is being defined here.
+\newcommand{\IndexMarker}{\ensuremath{^\vartriangle}}
+
 % Used for defining occurrence of phrase, with customized index entry.
 \newcommand{\IndexCustom}[2]{%
-  \leavevmode\marginpar{\ensuremath{\vartriangle}}\emph{#1}\index{#2}}
+  \leavevmode\marginpar{\IndexMarker}\emph{#1}\index{#2}}
 
 % Used for the defining occurrence of a local symbol.
 \newcommand{\DefineSymbol}[1]{%
@@ -196,7 +199,7 @@
 
 % Same appearance, but not adding an entry to the index.
 \newcommand{\NoIndex}[1]{%
-  \leavevmode\marginpar{\ensuremath{\vartriangle}}\emph{#1}}
+  \leavevmode\marginpar{\IndexMarker}\emph{#1}}
 
 % Mark a compile-time error in the margin.
 \newcommand{\Error}[1]{%

specification/dartLangSpec.tex

@@ -848,11 +848,11 @@ \section{Notation}
 \LMHash{}%
 The document contains an index at the end.
 Each entry in the index refers to a page number, $p$.
-On page $p$ there is a `$\diamond$' in the margin
+On page $p$ there is a `\IndexMarker{}' in the margin
 at the definition of the given indexed phrase,
 and the phrase itself is shown using \emph{this typeface}.
 We have hereby introduced the
-\Index{index marker $\diamond$}
+\Index{index marker \IndexMarker{}}
 itself.
 
 \LMHash{}%