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Add a replace action #226

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Add a replace action #226

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0c4b2de
working on replace action
oflatt Sep 6, 2023
1a38c57
imeplement replace
oflatt Sep 6, 2023
4176de6
basic replace test
oflatt Sep 6, 2023
c9b20c0
seminaive transform for replace
oflatt Sep 8, 2023
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37 changes: 37 additions & 0 deletions src/ast/desugar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -251,6 +251,32 @@ fn flatten_actions(actions: &Vec<Action>, desugar: &mut Desugar) -> Vec<NormActi
);
res.push(set);
}
Action::Replace {
old_constructor: constructor,
new_constructor: other_constructor,
old_args,
new_args,
new_output,
} => {
let replace = NormAction::Replace(
NormExpr::Call(
*constructor,
old_args
.iter()
.map(|ex| add_expr(ex.clone(), &mut res))
.collect(),
),
NormExpr::Call(
*other_constructor,
new_args
.iter()
.map(|ex| add_expr(ex.clone(), &mut res))
.collect(),
),
add_expr(new_output.clone(), &mut res),
);
res.push(replace);
}
Action::Extract(expr, variants) => {
let added = add_expr(expr.clone(), &mut res);
let added_variants = add_expr(variants.clone(), &mut res);
Expand Down Expand Up @@ -385,6 +411,17 @@ fn add_semi_naive_rule(desugar: &mut Desugar, rule: Rule) -> Option<Rule> {
new_head_atoms.push(Fact::Eq(vec![fresh_var, expr]));
};
}
Action::Replace { new_output, .. } => {
var_set.extend(new_output.vars());
if let Expr::Call(_, _) = new_output {
add_new_rule = true;

let fresh_symbol = desugar.get_fresh();
let fresh_var = Expr::Var(fresh_symbol);
let new_output = std::mem::replace(new_output, fresh_var.clone());
new_head_atoms.push(Fact::Eq(vec![fresh_var, new_output]));
};
}
Action::Let(symbol, expr) if var_set.contains(symbol) => {
var_set.extend(expr.vars());
if let Expr::Call(_, _) = expr {
Expand Down
127 changes: 127 additions & 0 deletions src/ast/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -743,6 +743,21 @@ pub enum Action {
Let(Symbol, Expr),
Set(Symbol, Vec<Expr>, Expr),
Delete(Symbol, Vec<Expr>),
/// Replace a row in a table with another row.
/// Equivalent to `delete` followed by `set`,
/// except that it is aware when the new row is
/// the same as the old and can therefore saturate
/// in this case.
///
/// If the constructors are different, simply deletes
/// from one table and adds to another.
Replace {
old_constructor: Symbol,
new_constructor: Symbol,
old_args: Vec<Expr>,
new_args: Vec<Expr>,
new_output: Expr,
},
Union(Expr, Expr),
Extract(Expr, Expr),
Panic(String),
Expand All @@ -758,6 +773,7 @@ pub enum NormAction {
Extract(Symbol, Symbol),
Set(NormExpr, Symbol),
Delete(NormExpr),
Replace(NormExpr, NormExpr, Symbol),
Union(Symbol, Symbol),
Panic(String),
}
Expand All @@ -779,6 +795,17 @@ impl NormAction {
NormAction::Delete(NormExpr::Call(symbol, args)) => {
Action::Delete(*symbol, args.iter().map(|s| Expr::Var(*s)).collect())
}
NormAction::Replace(
NormExpr::Call(head, body),
NormExpr::Call(head2, body2),
output,
) => Action::Replace {
old_constructor: *head,
new_constructor: *head2,
old_args: body.iter().map(|s| Expr::Var(*s)).collect(),
new_args: body2.iter().map(|s| Expr::Var(*s)).collect(),
new_output: Expr::Var(*output),
},
NormAction::Union(lhs, rhs) => Action::Union(Expr::Var(*lhs), Expr::Var(*rhs)),
NormAction::Panic(msg) => Action::Panic(msg.clone()),
}
Expand All @@ -790,6 +817,9 @@ impl NormAction {
NormAction::LetVar(symbol, other) => NormAction::LetVar(*symbol, *other),
NormAction::LetLit(symbol, lit) => NormAction::LetLit(*symbol, lit.clone()),
NormAction::Set(expr, other) => NormAction::Set(f(expr), *other),
NormAction::Replace(expr1, expr2, other) => {
NormAction::Replace(f(expr1), f(expr2), *other)
}
NormAction::Extract(var, variants) => NormAction::Extract(*var, *variants),
NormAction::Delete(expr) => NormAction::Delete(f(expr)),
NormAction::Union(lhs, rhs) => NormAction::Union(*lhs, *rhs),
Expand All @@ -810,6 +840,11 @@ impl NormAction {
NormAction::Set(expr, other) => {
NormAction::Set(expr.map_def_use(fvar, false), fvar(*other, false))
}
NormAction::Replace(expr1, expr2, other) => NormAction::Replace(
expr1.map_def_use(fvar, false),
expr2.map_def_use(fvar, false),
fvar(*other, false),
),
NormAction::Extract(var, variants) => {
NormAction::Extract(fvar(*var, false), fvar(*variants, false))
}
Expand All @@ -825,6 +860,20 @@ impl ToSexp for Action {
match self {
Action::Let(lhs, rhs) => list!("let", lhs, rhs),
Action::Set(lhs, args, rhs) => list!("set", list!(lhs, ++ args), rhs),
Action::Replace {
old_constructor: constructor,
new_constructor: other_constructor,
old_args,
new_args,
new_output,
} => {
list!(
"replace",
list!(constructor, ++ old_args),
list!(other_constructor, ++ new_args),
new_output
)
}
Action::Union(lhs, rhs) => list!("union", lhs, rhs),
Action::Delete(lhs, args) => list!("delete", list!(lhs, ++ args)),
Action::Extract(expr, variants) => list!("extract", expr, variants),
Expand All @@ -842,6 +891,27 @@ impl Action {
let right = f(rhs);
Action::Set(*lhs, args.iter().map(f).collect(), right)
}
Action::Replace {
old_constructor: constructor,
new_constructor: other_constructor,
old_args,
new_args,
new_output,
} => {
// use for loop because of borrow error
// with passing f to map
let mut mapped_old_args: Vec<Expr> = vec![];
for entry in old_args {
mapped_old_args.push(f(entry));
}
Action::Replace {
old_constructor: *constructor,
new_constructor: *other_constructor,
old_args: mapped_old_args,
new_output: f(new_output),
new_args: new_args.iter().map(f).collect(),
}
}
Action::Delete(lhs, args) => Action::Delete(*lhs, args.iter().map(f).collect()),
Action::Union(lhs, rhs) => Action::Union(f(lhs), f(rhs)),
Action::Extract(expr, variants) => Action::Extract(f(expr), f(variants)),
Expand All @@ -858,6 +928,19 @@ impl Action {
args.iter().map(|e| e.subst(canon)).collect(),
rhs.subst(canon),
),
Action::Replace {
old_constructor: constructor,
new_constructor: other_constructor,
old_args,
new_args,
new_output,
} => Action::Replace {
old_constructor: *constructor,
new_constructor: *other_constructor,
old_args: old_args.iter().map(|e| e.subst(canon)).collect(),
new_args: new_args.iter().map(|e| e.subst(canon)).collect(),
new_output: new_output.subst(canon),
},
Action::Delete(lhs, args) => {
Action::Delete(*lhs, args.iter().map(|e| e.subst(canon)).collect())
}
Expand Down Expand Up @@ -985,6 +1068,9 @@ impl NormRule {
res
}

// TODO this function isn't actually correct right now
// because actions can fail halfway-through.
// If we fix that bug, we can run this.
pub fn resugar_actions(&self, subst: &mut HashMap<Symbol, Expr>) -> Vec<Action> {
let mut used = HashSet::<Symbol>::default();
let mut head = Vec::<Action>::default();
Expand All @@ -1001,6 +1087,8 @@ impl NormRule {
let substituted = new_expr.subst(subst);

// TODO sometimes re-arranging actions is bad
// this is because actions can fail
// halfway through in the current semantics
if substituted.ast_size() > 1 {
head.push(Action::Let(*symbol, substituted));
} else {
Expand Down Expand Up @@ -1040,6 +1128,45 @@ impl NormRule {
_ => panic!("Expected call in set"),
}
}
NormAction::Replace(expr1, expr2, output_var) => {
let new_expr1 = expr1.to_expr();
new_expr1.map(&mut |subexpr| {
if let Expr::Var(v) = subexpr {
used.insert(*v);
}
subexpr.clone()
});
let new_expr2 = expr2.to_expr();
new_expr2.map(&mut |subexpr| {
if let Expr::Var(v) = subexpr {
used.insert(*v);
}
subexpr.clone()
});
let new_output = subst
.get(output_var)
.unwrap_or(&Expr::Var(*output_var))
.clone();
used.insert(*output_var);
let substituted1 = new_expr1.subst(subst);
let substituted2 = new_expr2.subst(subst);
match (substituted1, substituted2) {
(
Expr::Call(constructor, old_args),
Expr::Call(other_constructor, new_args),
) => {
assert!(constructor == other_constructor);
head.push(Action::Replace {
old_constructor: constructor,
new_constructor: other_constructor,
old_args,
new_args,
new_output,
});
}
_ => panic!("Expected call in replace"),
}
}
NormAction::Delete(expr) => {
let new_expr = expr.to_expr();
new_expr.map(&mut |subexpr| {
Expand Down
2 changes: 2 additions & 0 deletions src/ast/parse.lalrpop
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Expand Up @@ -107,6 +107,8 @@ Cost: Option<usize> = {
NonLetAction: Action = {
LParen "set" LParen <f: Ident> <args:Expr*> RParen <v:Expr> RParen => Action::Set ( f, args, v ),
LParen "delete" LParen <f: Ident> <args:Expr*> RParen RParen => Action::Delete ( f, args),
LParen "replace" LParen <old_constructor: Ident> <old_args:Expr*> RParen
LParen <new_constructor: Ident> <new_args:Expr*> RParen <new_output:Expr> RParen => Action::Replace { new_constructor, old_constructor, old_args, new_args, new_output},
LParen "union" <e1:Expr> <e2:Expr> RParen => Action::Union(<>),
LParen "panic" <msg:String> RParen => Action::Panic(msg),
LParen "extract" <expr:Expr> RParen => Action::Extract(expr, Expr::Lit(Literal::Int(0))),
Expand Down
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