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# Differences

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sav08:fixed-width_bitvectors [2008/03/13 11:28]
vkuncak
sav08:fixed-width_bitvectors [2015/04/21 17:30] (current)
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K ::= 0 | 1 | 2 | ...    K ::= 0 | 1 | 2 | ...

-Suppose we are given bounds for all integer variables and that they belong to $[0,​2^B]$.  ​+Suppose we are given bounds for all integer variables and that they belong to $[0,2^B-1]$.  ​

We present translation from $F$ to equisatisfiable $prop(F)$ in propositional logic. ​ That is, We present translation from $F$ to equisatisfiable $prop(F)$ in propositional logic. ​ That is,
-$+\begin{equation*} ​\exists x_1,​\ldots,​x_n.\ F ​\exists x_1,​\ldots,​x_n.\ F -$+\end{equation*}
is equivalent to is equivalent to
-$+\begin{equation*} ​\exists p_1,​\ldots,​p_m.\ prop(F) ​\exists p_1,​\ldots,​p_m.\ prop(F) -$+\end{equation*}
Where $FV(F)=\{x_1,​\ldots,​x_n\}$ and $FV(prop(F)) = \{p_1,​\ldots,​p_m\}$. Where $FV(F)=\{x_1,​\ldots,​x_n\}$ and $FV(prop(F)) = \{p_1,​\ldots,​p_m\}$.

-For each bounded integer variable $x \in [0,2^B]$ we introduce propositional variables corresponding to its binary representation.+For each bounded integer variable $x \in [0,2^B-1]$ we introduce propositional variables corresponding to its binary representation.

The constructions for operations correspond to implementing these operations in hardware circuits: The constructions for operations correspond to implementing these operations in hardware circuits:
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* shift for *   * shift for *
* comparator for <, =   * comparator for <, =
+
+Example: propositional formula expressing $x + y = z$ when $x,y,z \in [0,2^B-1]$.

Note that subtraction can be expressed using addition, similarly for / and %. Note that subtraction can be expressed using addition, similarly for / and %.