Specify behavior of e?.v++ and e?.v--

docs/language/dartLangSpec.tex

 \documentclass{article}
 \usepackage{epsfig}
 \usepackage{color}
 \usepackage{dart}
 \usepackage{bnf}
 \usepackage{hyperref}
 \usepackage{lmodern}
 \newcommand{\code}[1]{{\sf #1}}
 \title{Dart Programming Language  Specification \\
 {\large Version 1.10}}
@@ skipping 4994 matching lines @@
 {\bf incrementOperator:}`++';
       `-{}-'
     .
         
  \end{grammar}
  
 \LMHash{}
  A {\em postfix expression} is either a primary expression, a function, method or getter invocation, or an invocation of a postfix operator on an expression $e$.
 
 \LMHash{}
-A postfix expression of the form \code{$v$++}, where $v$ is an identifier, is equivalent to \code{()\{var r = $v$; $v$ = r + 1; return r\}()}.
+A postfix expression of the form \code{$v$++}, where $v$ is an identifier, is equivalent to \code{()\{\VAR{} r = $v$; $v$ = r + 1; \RETURN{} r\}()}.
 
 \rationale{The above ensures that if $v$ is a field, the getter gets called exactly once. Likewise in the cases below. 
 }
-%what about e?.x++ 
 
 \LMHash{}
 A postfix expression of the form \code{$C.v$ ++} is equivalent to 
 
-\code{()\{var r = $C.v$; $C.v$ = r + 1; return r\}()}.
+\code{()\{\VAR{} r = $C.v$; $C.v$ = r + 1; \RETURN{} r\}()}.
 
 \LMHash{}
 A postfix expression of the form \code{$e_1.v$++} is equivalent to 
 
-\code{(x)\{var r = x.v; x.v = r + 1; \RETURN{} r\}($e_1$)}.
+\code{(x)\{\VAR{} r = x.v; x.v = r + 1; \RETURN{} r\}($e_1$)}.
 
 \LMHash{}
 A postfix expression of the form \code{$e_1[e_2]$++},  is equivalent to 
 
-\code{(a, i)\{var r = a[i]; a[i] = r + 1; return r\}($e_1$, $e_2$)}.
+\code{(a, i)\{\VAR{} r = a[i]; a[i] = r + 1; \RETURN{} r\}($e_1$, $e_2$)}.
 
 \LMHash{}
 A postfix expression of the form \code{$v$-{}-}, where $v$ is an identifier, is equivalent to 
 
-\code{()\{var r = $v$; $v$ = r - 1; return r\}()}.
+\code{()\{\VAR{} r = $v$; $v$ = r - 1; \RETURN{} r\}()}.
 
 \LMHash{}
 A postfix expression of the form \code{$C.v$-{}-} is equivalent to 
 
-\code{()\{var r = $C.v$; $C.v$ = r - 1; return r\}()}.
+\code{()\{\VAR{} r = $C.v$; $C.v$ = r - 1; \RETURN{} r\}()}.
 
 \LMHash{}
 A postfix expression of the form \code{$e_1.v$-{}-} is equivalent to 
 
-\code{(x)\{var r = x.v; x.v = r - 1; \RETURN{} r\}($e_1$)}.
+\code{(x)\{\VAR{} r = x.v; x.v = r - 1; \RETURN{} r\}($e_1$)}.
 
 \LMHash{}
 A postfix expression of the form \code{$e_1[e_2]$-{}-},  is equivalent to 
 
-\code{(a, i)\{var r = a[i]; a[i] = r - 1; return r\}($e_1$, $e_2$)}.
- 
+\code{(a, i)\{\VAR{} r = a[i]; a[i] = r - 1; \RETURN{} r\}($e_1$, $e_2$)}.
+
+\LMHash{}
+A postfix expression of the form \code{$e_1?.v$++} is equivalent to 
+
+\code{((x) =$>$ x == \NULL? \NULL : x.v++)($e_1$)}.
+
+\LMHash{}
+A postfix expression of the form \code{$e_1?.v$-{}-} is equivalent to 
+
+\code{((x) =$>$ x == \NULL? \NULL : x.v-{}-)($e_1$)}.
+
 
 \subsection{ Assignable Expressions}
 \LMLabel{assignableExpressions}
 
 \LMHash{}
 Assignable expressions are expressions that can appear on the left hand side of an assignment.
 This section describes how to evaluate these expressions when they do not constitute the complete left hand side of an assignment.
 
 \rationale{
 Of course, if assignable expressions always appeared {\em as} the left hand side, one would have no need for their value, and the rules for evaluating them would be unnecessary. However,  assignable expressions can be subexpressions of other expressions and therefore must be evaluated.
@@ skipping 2731 matching lines @@
 
 The invariant that each normative paragraph is associated with a line
 containing the text \LMHash{} should be maintained.  Extra occurrences
 of \LMHash{} can be added if needed, e.g., in order to make
 individual \item{}s in itemized lists addressable.  Each \LM.. command
 must occur on a separate line.  \LMHash{} must occur immediately
 before the associated paragraph, and \LMLabel must occur immediately
 after the associated \section{}, \subsection{} etc.
 
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