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use std::fmt::{self, Debug}; use std::hash::Hash; use std::rc::Rc; use smallvec::SmallVec; use symbolic_expressions::Sexp; use crate::unionfind::UnionFind; /// The type of an eclass id in the [`EGraph`](struct.EGraph.html) pub type Id = u32; /// An operator from the user-defined [`Language`] with some children. /// /// An [`ENode`] is operator from the user-provided [`Language`] with /// zero or more children. /// Note that [`ENode`] is generic over both the [`Language`] and the /// type of the children. /// In the typical setting (inside and [`EClass`]), the children of an /// [`ENode`] are elcass [`Id`]s, so the second generic parameter /// defaults to [`Id`]. /// In other cases ([cost functions][cf] or [metadata]), the generic /// parameter may be something else. /// /// [`EGraph`]: struct.EGraph.html /// [`EClass`]: struct.EClass.html /// [`ENode`]: struct.ENode.html /// /// [`Id`]: type.Id.html /// [`Language`]: trait.Language.html /// [cf]: trait.CostFunction.html /// [metadata]: trait.Metadata.html #[derive(Debug, PartialEq, Eq, Hash, Clone)] pub struct ENode<O, Child = Id> { /// The operator from the user-defined [`Language`](trait.Language.html) pub op: O, /// The children of the [`ENode`](struct.ENode.html). /// In most cases, the child type is [`Id`](type.Id.html). pub children: SmallVec<[Child; 2]>, } type Inner<L> = ENode<L, RecExpr<L>>; /// A recursive expression from a user-defined [`Language`]. /// /// This is type is essentially an [`ENode`] whose children are /// [`RecExpr`]s. This is resource counted with [`Rc`], so it's cheap /// to clone. /// /// If the `serde-1` feature is enabled, this implements /// [`serde::Serialize`][ser] by pretty-printing with /// [`self.pretty(80)`][pretty]. /// /// [`ENode`]: struct.ENode.html /// [`RecExpr`]: struct.RecExpr.html /// [`Language`]: trait.Language.html /// [ser]: https://docs.rs/serde/latest/serde/trait.Serialize.html /// [pretty]: struct.RecExpr.html#method.pretty /// [`Rc`]: https://doc.rust-lang.org/std/rc/struct.Rc.html #[derive(Debug, PartialEq, Eq, Hash, Clone)] pub struct RecExpr<L> { rc: Rc<Inner<L>>, } #[cfg(feature = "serde-1")] impl<L: Language + fmt::Display> serde::Serialize for RecExpr<L> { fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: serde::Serializer, { // 3 is the number of fields in the struct. let s = self.pretty(80); serializer.serialize_str(&s) } } impl<L> From<Inner<L>> for RecExpr<L> { fn from(inner: Inner<L>) -> Self { let rc = Rc::new(inner); RecExpr { rc } } } impl<L> std::borrow::Borrow<Inner<L>> for RecExpr<L> { fn borrow(&self) -> &Inner<L> { &self.rc } } impl<L> AsRef<Inner<L>> for RecExpr<L> { fn as_ref(&self) -> &Inner<L> { &self.rc } } impl<L: Language + fmt::Display> RecExpr<L> { fn to_sexp(&self) -> Sexp { let e = self.as_ref(); let mut vec: Vec<_> = e.children.iter().map(Self::to_sexp).collect(); let op = Sexp::String(e.op.to_string()); if vec.is_empty() { op } else { vec.insert(0, op); Sexp::List(vec) } } /// Pretty print with a maximum line length. /// /// This gives you a nice, indented, pretty-printed s-expression. /// /// # Example /// ``` /// # use egg::*; /// define_language! { /// enum FooLanguage { /// Num(i32), /// Add = "+", /// Mul = "*", /// Symbol(String), /// } /// } /// /// let e: RecExpr<FooLanguage> = "(* (+ 2 2) (+ x y))".parse().unwrap(); /// assert_eq!(e.pretty(10), " /// (* /// (+ 2 2) /// (+ x y)) /// ".trim()); /// ``` pub fn pretty(&self, width: usize) -> String { use std::fmt::{Result, Write}; let sexp = self.to_sexp(); fn pp(buf: &mut String, sexp: &Sexp, width: usize, level: usize) -> Result { if let Sexp::List(list) = sexp { let indent = sexp.to_string().len() > width; write!(buf, "(")?; for (i, val) in list.iter().enumerate() { if indent && i > 0 { writeln!(buf)?; for _ in 0..level { write!(buf, " ")?; } } pp(buf, val, width, level + 1)?; if !indent && i < list.len() - 1 { write!(buf, " ")?; } } write!(buf, ")")?; Ok(()) } else { // I don't care about quotes write!(buf, "{}", sexp.to_string().trim_matches('"')) } } let mut buf = String::new(); pp(&mut buf, &sexp, width, 1).unwrap(); buf } } impl<L: Language, Child> ENode<L, Child> { /// Create a new [`ENode`] with no children. /// Equivalent to calling [`ENode::new`](#method.new) with no /// children. /// /// [`ENode`]: struct.ENode.html #[inline(always)] pub fn leaf(op: L) -> Self { ENode::new(op, vec![]) } /// Create a new [`ENode`]. /// /// [`ENode`]: struct.ENode.html #[inline(always)] pub fn new<I>(op: L, children: I) -> Self where I: IntoIterator<Item = Child>, { let children = children.into_iter().collect(); ENode { op, children } } /// Try to create an [`ENode`] with a falliable child iterator. /// /// # Example /// ``` /// # use egg::*; /// define_language! { /// enum Math { /// Num(i32), /// Add = "+", /// Mul = "*", /// } /// } /// /// // This is obviously silly, but maybe you have some more /// // complex function /// fn non_neg(i: i32) -> Result<u32, String> { /// if i >= 0 { /// Ok(i as u32) /// } else { /// Err(format!("{} is less than 0", i)) /// } /// } /// let r1: Result<ENode<Math, u32>, String> = ENode::try_new( /// Math::Add, /// vec![non_neg(1), non_neg(8)] /// ); /// let r2: Result<ENode<Math, u32>, String> = ENode::try_new( /// Math::Add, /// vec![non_neg(-1), non_neg(8)] /// ); /// assert_eq!(r1, Ok(enode!(Math::Add, 1, 8))); /// assert_eq!(r2, Err("-1 is less than 0".into())); /// ``` /// /// [`ENode`]: struct.ENode.html #[inline(always)] pub fn try_new<Error, I>(op: L, children: I) -> Result<Self, Error> where I: IntoIterator<Item = Result<Child, Error>>, { let c: Result<_, Error> = children.into_iter().collect(); c.map(|children| ENode { op, children }) } /// Create a new [`ENode`] by mapping a function over the children. /// /// `enode.map_children(f)` is equivalent to: /// ``` /// # use egg::*; /// # let enode = ENode::<String, i32>::leaf("h".into()); /// # let f = |x| x; /// # assert_eq!(enode, /// ENode::new( /// enode.op.clone(), /// enode.children.iter().cloned().map(f), /// ) /// # ); /// ``` /// /// [`ENode`]: struct.ENode.html #[inline(always)] pub fn map_children<Child2, F>(&self, mut f: F) -> ENode<L, Child2> where Child: Clone, F: FnMut(Child) -> Child2, { let some_f = |child| Result::<Child2, std::convert::Infallible>::Ok(f(child)); self.map_children_result(some_f).unwrap() } /// Create a new [`ENode`] by mapping a falliable function over /// the children. /// /// `enode.map_children_result(f)` is equivalent to: /// ``` /// # use egg::*; /// # let enode = ENode::<String, i32>::leaf("h".into()); /// # let f = |x| -> Result<i32, ()> { Ok(x) }; /// # assert_eq!(enode, /// ENode::try_new( /// enode.op.clone(), /// enode.children.iter().cloned().map(f), /// ) /// # .unwrap()); /// ``` /// /// [`ENode`]: struct.ENode.html #[inline(always)] pub fn map_children_result<Child2, F, Error>(&self, f: F) -> Result<ENode<L, Child2>, Error> where Child: Clone, F: FnMut(Child) -> Result<Child2, Error>, { ENode::try_new(self.op.clone(), self.children.iter().cloned().map(f)) } } impl<L: Language> ENode<L> { pub(crate) fn update_ids<V>(&self, unionfind: &UnionFind<Id, V>) -> Self { self.map_children(|id| unionfind.find(id)) } } /// Trait defines a Language whose terms will be in the [`EGraph`]. /// /// Typically, you'll want your language to implement [`FromStr`] and /// [`Display`] so parsing and printing works. /// Check out the [`define_language!`] macro for an easy way to create /// a [`Language`]. /// /// [`String`] implements [`Language`] for quick use cases. /// /// [`define_language!`]: macro.define_language.html /// [`Language`]: trait.Language.html /// [`EGraph`]: struct.EGraph.html /// [`String`]: https://doc.rust-lang.org/std/string/struct.String.html /// [`FromStr`]: https://doc.rust-lang.org/std/str/trait.FromStr.html /// [`Display`]: https://doc.rust-lang.org/std/fmt/trait.Display.html pub trait Language: Debug + PartialEq + Eq + Hash + Clone + 'static {} impl Language for String {}