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Fix the binding of empty Or formulas in the TseitinEncoder #67

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merged 1 commit into from
Aug 19, 2024
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Fix the binding of empty Or formulas in the TseitinEncoder #67

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26 changes: 25 additions & 1 deletion crates/pindakaas/src/propositional_logic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,11 @@ impl Formula {
}
Formula::Or(sub) => {
match sub.len() {
0 => return Err(Unsatisfiable),
0 => {
let name = name.unwrap_or_else(|| db.new_var().into());
db.add_clause([!name])?;
name
}
1 => return sub[0].bind(db, name),
_ => {
let name = name.unwrap_or_else(|| db.new_var().into());
Expand Down Expand Up @@ -365,6 +369,16 @@ mod tests {
=> vec![lits![-1, -2, 3], lits![1, -3], lits![2, -3]],
vec![lits![1, 2, 3], lits![-1, 2, -3], lits![-1, -2, -3], lits![1, -2, -3]]
);
// Regression test: empty and
assert_enc_sol!(
TseitinEncoder,
1,
&Formula::Equiv(vec![
Formula::Atom(1.into()),
Formula::And(vec![])
])
=> vec![lits![1]], vec![lits![1]]
);
}

#[test]
Expand Down Expand Up @@ -393,6 +407,16 @@ mod tests {
=> vec![lits![1, 2, -3], lits![-1, 3], lits![-2, 3]],
vec![lits![1, 2, 3], lits![-1, 2, 3], lits![-1, -2, -3], lits![1, -2, 3]]
);
// Regression test: empty or
assert_enc_sol!(
TseitinEncoder,
1,
&Formula::Equiv(vec![
Formula::Atom(1.into()),
Formula::Or(vec![])
])
=> vec![lits![-1]], vec![lits![-1]]
);
}

#[test]
Expand Down
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