Révision 242 CSL17/preliminaries.tex

preliminaries.tex (revision 242)
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	%\item $\bit(l;x)$ returns the $\mode l$th bit of $x$.
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	\item We can define the function $\bit(l;x)$ which returns the $|l|$th least significant bit of $x$. For instance $\bit(11;1011)=0$.
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	For that let us first define the function $\shorten(l;x)$ which returns the $|x|- |l|$ prefix of $x$, as follows:
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	For that let us first define the function $\shorten(l;x)$ which returns the $|x|- |l|+1$ prefix of $x$, as follows:
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	\begin{eqnarray*}
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	\shorten(\epsilon;x) &=&x\\
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	\shorten(0;x) &=&x\\
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	\shorten(\succ{i}l;x) &=&p(;\shorten(l;x))
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	\end{eqnarray*}
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	Then we define $\bit(l;x)$  as follows:
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	$$\bit(l;x)=C(;\shorten(pl;x),\epsilon,0,1).$$
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	$$\bit(l;x)=C(;\shorten(l;x),0,1).$$
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	\end{itemize}
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	\end{example}
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