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Update specification.tex

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Dale Weiler 2013-04-08 00:05:55 -03:00
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@ -707,6 +707,52 @@ those of the unparenthesized expression. It is an lvalue, a function designator
void expression if the unparenthesized expression is, respectively, an lvalue, a
function designator, or a void expression.
%% ->-> Constant expressions %%
\subsubsection{Constant expressions}
\paragraph*{Syntax}
\begin{lstlisting}[language=bnf]
constant-expression ::= conditional-expression
\end{lstlisting}
\paragraph*{Description}
A constant expression can be evaluated during translation rather than runtime, and
accordingly may be used in any place that a constant may be.
\paragraph*{Constraints}
\begin{itemize}
\item Constant expressions shall not contain assignment, increment, decrement,
function-call, or comma operators, except when contained within a subexpression
that is not evaluated.
\item Each constant expression shall evaluate to a constant that is in range of
representable values for its type.
\end{itemize}
\paragraph*{Semantics}
An expression that evaluates to a constant is required in several contexts. If a floating
point expression is evaluated in the translation environment, the arithmetic precision range
shall be as great is if the expression were being evaluated in the execution environment.
\linebreak
An integer constant expression shall have integer type and shall only have operands that
are integer constants, enumeration constants, character constants, and floating constants
that are the immediate operand of casts. Cast operators in an integer constant expression
shall only convert arithmetic types to integer types.
\linebreak
More latitude is permitted for constant expressions in initializers. Such a constant expression
shall be, or evaluate to an arithmetic constant expression.
\linebreak
An arithmetic constant expression shall have arithmetic type and shall only have operands that
are integer constants, floating constants, enumeration constants, and character constants. Cast
operators in an arithmetic constant expression shall only convert arithmetic types to arithmetic
types.
\linebreak
An implementation may accept other forms of constant expressions.
\linebreak
The semantic rules for the evaluation of a constant expression are the same as for nonconstant
expressions.
\bibliographystyle{abbrv}
\bibliography{main}