Merge pull request modelica#3415 from HansOlsson/ClearerReinit

Generalize/clarify reinit

chapters/equations.tex

@@ -442,7 +442,7 @@ \subsection{reinit}\label{reinit}
 \end{lstlisting}
 
 The operator reinitializes \lstinline!x! with \lstinline!expr! at an event instant.
-\lstinline!x! is a \lstinline!Real! variable (or an array of \lstinline!Real! variables) that must be selected as a state (resp., states), i.e., \lstinline!reinit! on \lstinline!x! implies \lstinline!stateSelect = StateSelect.always! on \lstinline!x!.
+\lstinline!x! is a component-reference (where any subscripts are evaluable) referring to a \lstinline!Real! variable (or an array of \lstinline!Real! variables) that must be selected as a state (resp., states), i.e., \lstinline!reinit! on \lstinline!x! implies \lstinline!stateSelect = StateSelect.always! on \lstinline!x!.
 \lstinline!expr! needs to be type-compatible with \lstinline!x!.
 For any given variable (possibly an array variable), \lstinline!reinit! can only be applied (either to an individual variable or to a part of an array variable) in one \lstinline!when!-equation (applying \lstinline!reinit! to a variable in several \lstinline!when!- or \lstinline!elsewhen!-clauses of the same \lstinline!when!-equation is allowed).
 If there are multiple \lstinline!reinit! for a variable inside the same \lstinline!when!- or \lstinline!elsewhen!-clause, they must appear in different branches of an \lstinline!if!-equation (in order that at most one \lstinline!reinit! for the variable is active at any event).