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\begin{figure}
\begin{syntax}
\syntaxclass{Statements:}
s & ::= & "skip" & empty statement \\
& \alt & a & expression evaluation\\
& \alt & a_1 = a_2 & assignment \\
& \alt & s_1 ; s_2 & sequence \\
& \alt & "if"(a) ~ s_1 ~ "else" ~ s_2 & conditional \\
& \alt & "switch"(a) \ls & switch \\
& \alt & "while"(a) ~ s & ``while'' loop \\
& \alt & "do" ~ s ~ "while" (a) & ``do'' loop \\
& \alt & "for"(s_1, a, s_2)~s & ``for'' loop \\
& \alt & "break" & exit from the current loop \\
& \alt & "continue" & next iteration of the current loop\\
& \alt & "return"~\opt a & return from current function
%
\syntaxclass{Switch branches:}
\ls & ::= & "default" (s) & default case switch \\
& \alt & "case" (n, s, \ls) & non default case switch
%
\syntaxclass{Functions:}
\cfn & ::= & (\ldots \id_i: \tau_i \ldots): \tau & header\\
& & \{ \ldots \tau_j~ \id_j ; \ldots & local variables \\
& & ~ s ~ \} & function body
%
\syntaxclass{Function signatures:}
\sig & ::= & \ldots \tau_i \ldots \tau & \\
%
\syntaxclass{Function definitions:}
\fn & ::= & \cfn & Clight (internal) function\\
& \alt & <\id ~ \sig> & external function (system call)
%
\syntaxclass{Whole programs:}
{\it init} & ::= & \ldots & \\
\prog & ::= & \ldots (\id_i,{{{\it init}}_i}^*): \tau_i \ldots & global variables (names, \\
& & &initialized data and types) \\
& & \ldots \id_j = \fn_j \ldots & functions (names and definitions) \\
& & \id_{main} & entry point
\end{syntax}
\caption{Abstract syntax of Clight (statements, functions and programs). }
\label{fig:syntax2}
\end{figure}
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