broken state

src/factorization.rs

@@ -0,0 +1,249 @@
+use core::fmt;
+use std::{cmp::Ordering, fmt::Display};
+use crate::language::{EquationLanguage, Rational, RATIONAL_ONE, RATIONAL_ZERO};
+use egg::{Id, RecExpr};
+
+
+#[derive(Debug,Clone,Copy)]
+pub struct PolyStat {
+	degree: usize,
+	factors: usize, // non-constant factors
+	ops: usize,
+	monomial: bool,
+	sum_of_monomials: bool,
+	monic: bool,
+	factorized: bool, // a product of monic polynomials and at least one constant
+}
+
+#[derive(Debug,Clone,Copy)]
+pub enum FactorizationCost {
+	UnwantedOps,
+	Polynomial(PolyStat)
+}
+
+fn score(cost: FactorizationCost) -> usize {
+	match cost {
+		FactorizationCost::UnwantedOps => 10000,
+		FactorizationCost::Polynomial(p) =>
+			if !p.factorized {
+				1000 + p.ops
+			} else {
+				100 * (9 - p.factors) + p.ops
+			},
+	}
+}
+
+impl PartialEq for FactorizationCost {
+	fn eq(&self, other: &Self) -> bool {
+		score(*self) == score(*other)
+	}
+}
+
+impl PartialOrd for FactorizationCost {
+	fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+		usize::partial_cmp(&score(*self), &score(*other))
+	}
+}
+
+pub struct FactorizationCostFn;
+impl egg::CostFunction<EquationLanguage> for FactorizationCostFn {
+	type Cost = FactorizationCost;
+
+	fn cost<C>(&mut self, enode: &EquationLanguage, mut costs: C) -> Self::Cost
+	where
+		C: FnMut(Id) -> Self::Cost,
+	{
+		match enode {
+			EquationLanguage::Add([a,b]) => {
+				match (costs(*a), costs(*b)) {
+					(FactorizationCost::Polynomial(p1),FactorizationCost::Polynomial(p2)) => {
+						// we only ever want to add monomials
+						let result_monic = if p1.degree > p2.degree {
+							p1.monic
+						} else if p2.degree > p1.degree {
+							p2.monic
+						} else {
+							false
+						};
+
+						if !p1.sum_of_monomials || !p2.sum_of_monomials {
+							FactorizationCost::UnwantedOps
+						} else {
+							FactorizationCost::Polynomial(PolyStat {
+								degree: usize::max(p1.degree, p2.degree),
+								factors: 1,
+								ops: p1.ops + p2.ops,
+								monomial: false,
+								sum_of_monomials: p1.sum_of_monomials && p2.sum_of_monomials,
+								monic: result_monic,
+								factorized: result_monic,
+							})
+						}
+					},
+					_ => FactorizationCost::UnwantedOps
+				}
+			},
+			EquationLanguage::Mul([a,b]) => {
+				match (costs(*a), costs(*b)) {
+					(FactorizationCost::Polynomial(p1), FactorizationCost::Polynomial(p2)) => {
+						FactorizationCost::Polynomial(PolyStat {
+							degree: p1.degree + p2.degree,
+							factors: p1.factors + p2.factors,
+							ops: p1.ops + p2.ops,
+							monomial: p1.monomial && p2.monomial,
+							sum_of_monomials: p1.monomial && p2.monomial,
+							monic: p1.monic && p2.monic,
+							factorized: (p1.monic && p2.factorized) || (p2.monic && p1.factorized)
+						})
+					},
+					_ => FactorizationCost::UnwantedOps
+				}
+			},
+			EquationLanguage::Num(c) => {
+				FactorizationCost::Polynomial(PolyStat {
+					degree: 0,
+					factors: 0,
+					ops: 0,
+					monomial: true,
+					sum_of_monomials: true,
+					monic: false,
+					factorized: true
+				})
+			},
+			EquationLanguage::Unknown => {
+				FactorizationCost::Polynomial(PolyStat {
+					degree: 1,
+					factors: 1,
+					ops: 0,
+					monomial: true,
+					sum_of_monomials: true,
+					monic: true,
+					factorized: true
+				})
+			},
+			_ => FactorizationCost::UnwantedOps,
+		}
+	}
+}
+
+#[derive(Debug,Clone)]
+pub struct Factorization {
+	pub constant_factor: Rational,
+	pub polynomials: Vec<Vec<Rational>>,
+}
+
+impl Display for Factorization {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		if self.constant_factor != RATIONAL_ONE {
+			write!(f, "{}", self.constant_factor)?;
+		}
+
+		for poly in &self.polynomials {
+			write!(f, "(")?;
+			for (deg, coeff) in poly.iter().enumerate() {
+				if deg == 0 {
+					write!(f, "{}", coeff)?;
+				} else if deg == 1 {
+					write!(f, " + {}x", coeff)?;
+				} else {
+					write!(f, " + {}x^{}", coeff, deg)?;
+				}
+			}
+			write!(f, ")")?;
+		}
+
+		Ok(())
+	}
+}
+
+pub fn extract_factorization(expr: &RecExpr<EquationLanguage>) -> Factorization {
+	let root_id: Id = Id::from(expr.as_ref().len()-1);
+
+	let mut constant_factor: Option<Rational> = None;
+	let mut factors: Vec<Vec<Rational>> = Vec::new();
+	let mut todo: Vec<Id> = Vec::new();
+	todo.push(root_id);
+
+	while todo.len() > 0 {
+		let id = todo.pop().unwrap();
+
+		match &expr[id] {
+			EquationLanguage::Mul([a,b]) => {
+				todo.push(*a);
+				todo.push(*b);
+			},
+			EquationLanguage::Num(x) => {
+				assert!(constant_factor.is_none());
+				constant_factor = Some(x.clone());
+			},
+			_ => {
+				factors.push(extract_polynomial(expr, id));
+			}
+		}
+	}
+
+	Factorization {
+		constant_factor: constant_factor.unwrap_or_else(||RATIONAL_ONE.clone()),
+		polynomials: factors
+	}
+}
+
+fn extract_polynomial(expr: &RecExpr<EquationLanguage>, id: Id) -> Vec<Rational> {
+	let mut result: Vec<Rational> = Vec::new();
+	let mut todo: Vec<Id> = Vec::new();
+	todo.push(id);
+
+	while todo.len() > 0 {
+		let id = todo.pop().unwrap();
+
+		match &expr[id] {
+			EquationLanguage::Add([a,b]) => {
+				todo.push(*a);
+				todo.push(*b);
+			},
+			_ => {
+				let (deg, coeff) = extract_monomial(expr, id);
+				result.resize(result.len().max(deg), RATIONAL_ZERO.clone());
+
+				if result.len() <= deg {
+					result.push(coeff);
+				} else {
+					assert!(result[deg] == RATIONAL_ZERO);
+					result[deg] = coeff;
+				}
+			}
+		}
+	}
+
+	result
+}
+
+fn extract_monomial(expr: &RecExpr<EquationLanguage>, id: Id) -> (usize, Rational) {
+	let mut coeff: Option<Rational> = None;
+	let mut deg: usize = 0;
+	let mut todo: Vec<Id> = Vec::new();
+	todo.push(id);
+
+	while todo.len() > 0 {
+		let id = todo.pop().unwrap();
+
+		match &expr[id] {
+			EquationLanguage::Unknown => {
+				deg += 1;
+			},
+			EquationLanguage::Mul([a,b]) => {
+				todo.push(*a);
+				todo.push(*b);
+			},
+			EquationLanguage::Num(x) => {
+				assert!(coeff.is_none());
+				coeff = Some(x.clone());
+			},
+			_ => {
+				panic!("Not a rational polynomial in normal form!");
+			}
+		}
+	}
+
+	(deg, coeff.unwrap_or_else(||RATIONAL_ONE.clone()))
+}

src/lib.rs

@@ -1,3 +1,5 @@
 pub mod language;
 pub mod normal_form;
 pub mod parse;
+pub mod factorization;
+pub mod output;

src/main.rs

@@ -1,24 +1,35 @@
-use egg::{Extractor, Pattern, RecExpr, Runner};
-use solveq::language::{RULES, EquationLanguage, PlusTimesCostFn, FactorizationCostFn};
+use egg::{AstSize, EGraph, Extractor, Id, Pattern, RecExpr, Runner};
+use solveq::factorization::{extract_factorization, FactorizationCost, FactorizationCostFn};
+use solveq::language::{ConstantFold, EquationLanguage, FactorizationCostFn, PlusTimesCostFn, Rational, RULES};
 use solveq::normal_form::analyze3;
 use solveq::parse::parse_equation;
+use solveq::output::print_term;
 
 static TEST_EQUATIONS: &[&str] = &[
-	"(x + 50) * 10 - 150 - 100",
-	"(x - 2) * (x + 2) - 0",
-	"x ^ 2 - 4",
-	"x ^ 2 - 2 - 0",
-	"x ^ 2 - (2 * x + 15)",
-	"(x ^ 2 - 2 * x - 15) * (x + 5) - 0",
-	"x ^ 3 + 3 * x ^ 2 - 25 * x - 75 - 0",
+	"(x + 50) * 10 - 150 = 100",
+	"(x - 2) * (x + 2) = 0",
+	"x ^ 2 = 4",
+	"x ^ 2 - 2 = 0",
+	"x ^ 2 = 2 * x + 15",
+	"(x ^ 2 - 2 * x - 15) * (x + 5) = 0",
+	"x ^ 3 + 3 * x ^ 2 - 25 * x - 75 = 0",
 ];
 
-fn main() {
-	for eq in TEST_EQUATIONS {
-		let start = parse_equation(*eq).unwrap();
 
-	//	println!("{:?}", &start);
-	// do transformation to left - right = 0
+fn main() {
+	let expr: RecExpr<EquationLanguage> = "(* x (+ x -2))".parse().unwrap();
+	println!("{:?}", get_expression_cost(&expr));
+
+	for eq in TEST_EQUATIONS {
+		println!("Equation: {}", *eq);
+
+		let mut start = parse_equation(*eq).unwrap();
+		let root_id = Id::from(start.as_ref().len()-1);
+		let EquationLanguage::Equals([left, right]) = start[root_id]
+		else { panic!("Not an equation without an equals sign!"); };
+		start[root_id] = EquationLanguage::Sub([left, right]);
+
+		println!("Parsed: {}", &start);
 
 		let mut runner = Runner::default()
 			.with_explanations_enabled()
@@ -29,198 +40,55 @@ fn main() {
 
 		let (best_cost, best_expr) = extractor.find_best(runner.roots[0]);
 
-		println!("{}", start);
-		println!("{:?} {:?}", best_cost, <RecExpr<EquationLanguage> as AsRef<[EquationLanguage]>>::as_ref(&best_expr));
+//		println!("{:?} {:?}", best_cost, <RecExpr<EquationLanguage> as AsRef<[EquationLanguage]>>::as_ref(&best_expr));
 
+		println!("Best expresssion: {} {:?}", best_expr, best_cost);
 
-		println!("");
-	}
-
-//	let root = runner.roots[0];
-//		let egraph = &runner.egraph;
-//	let pattern: Pattern<EquationLanguage> = "(+ (* ?a (* x x)) ?c)".parse().unwrap();
-//	let matches = pattern.search(&egraph);
-
-
-
-//	println!("{:?}", egraph.classes().count());
-
-	// Analyze
-//	analyze3(egraph, runner.roots[0]);
-
-	/*
-	for class in egraph.classes() {
-		if monic_nonconst_polynomial(egraph, class.id).is_some() {
-			let (_, best_expr) = extractor.find_best(class.id);
-			println!("Monomial: {}", best_expr);
-		}
-	}
-
-	println!("{:?}", &matches);
-	*/
-
+		let factorization = extract_factorization(&best_expr);
 
 //		println!("{}", runner.explain_equivalence(&start, &best_expr).get_flat_string());
+
+		println!("Factorized normal form: {}", factorization);
+
+		let mut solutions: Vec<String> = Vec::new();
+		for poly in &factorization.polynomials {
+			if poly.len() == 2 { // linear factor
+				let Rational { num, denom } = &poly[0];
+				solutions.push(format!("x = {}", Rational { num: -*num, denom: *denom }));
+			} else if poly.len() == 3 { // quadratic factor
+				let Rational { num: num0, denom: denom0 } = &poly[0];
+				let Rational { num: num1, denom: denom1 } = &poly[1];
+
+				let sol1 = format!("- ({num1})/(2 * ({denom1})) + ((({num1})/(2 * ({denom1}))) ^ 2 - ({num0}) / ({denom0})) ^ (1/2)");
+				let sol2 = format!("- ({num1})/(2 * ({denom1})) - ((({num1})/(2 * ({denom1}))) ^ 2 - ({num0}) / ({denom0})) ^ (1/2)");
+
+				let expr = parse_equation(&sol1).unwrap();
+				let runner = Runner::default()
+					.with_expr(&expr)
+					.run(&*RULES);
+				let extractor = Extractor::new(&runner.egraph, AstSize);
+				let (_, simplified_expr) = extractor.find_best(runner.roots[0]);
+				solutions.push(format!("x = {}", print_term(&simplified_expr)));
+
+				let expr = parse_equation(&sol2).unwrap();
+				let runner = Runner::default()
+					.with_expr(&expr)
+					.run(&*RULES);
+				let extractor = Extractor::new(&runner.egraph, AstSize);
+				let (_, simplified_expr) = extractor.find_best(runner.roots[0]);
+				solutions.push(format!("x = {}", print_term(&simplified_expr)));
+			}
+		}
+
+		println!("Solutions: {{ {} }}", solutions.join(", "));
+		println!("");
+	}
 }
 
-
-/*
-fn power_of_x(egraph: &EGraph, eclass: Id) -> Option<usize> {
-	for n in &egraph[eclass].nodes {
-		match *n {
-			EquationLanguage::Unknown => { return Some(1) },
-			EquationLanguage::Mul([a,b]) => {
-				let Some(left) = power_of_x(egraph, a) else { continue };
-				let Some(right) = power_of_x(egraph, b) else { continue };
-				return Some(left + right);
-			},
-			_ => {}
-		}
-	}
-	None
+fn get_expression_cost(expr: &RecExpr<EquationLanguage>) -> FactorizationCost {
+    let mut egraph = EGraph::new(ConstantFold::default());
+    let id = egraph.add_expr(expr);
+    let extractor = Extractor::new(&egraph, FactorizationCostFn);
+    let (cost, _) = extractor.find_best(id);
+    cost
 }
-
-fn monomial(egraph: &EGraph, eclass: Id) -> Option<(usize, Rational)> {
-	if let Some(deg) = power_of_x(egraph, eclass) {
-		return Some((deg, RATIONAL_ONE.clone()));
-	}
-
-	for n in &egraph[eclass].nodes {
-		match *n {
-			EquationLanguage::Mul([a,b]) => {
-				let Some(coeff) = egraph[a].data.clone() else { continue };
-				let Some(deg) = power_of_x(egraph, b) else { continue };
-				return Some((deg, coeff));
-			},
-			_ => {}
-		}
-	}
-	None
-}
-
-
-// this is either a power_of_x, or a sum of this and a monomial
-fn monic_nonconst_polynomial(egraph: &EGraph, eclass: Id) -> Option<Vec<Rational>> {
-	let mut result: Vec<Rational> = Vec::new();
-
-	if let Some(deg) = power_of_x(egraph, eclass) {
-		result.resize(deg - 1, RATIONAL_ZERO);
-		result.push(RATIONAL_ONE.clone());
-		return Some(result);
-	}
-
-	for n in &egraph[eclass].nodes {
-		match *n {
-			EquationLanguage::Add([a,b]) => {
-				let Some(mut leading) = monic_nonconst_polynomial(egraph, a)
-				else { continue };
-				let Some(addon) = monomial(egraph, b)
-				else { continue };
-
-				if leading.len() <= addon.0 || leading[addon.0] != RATIONAL_ZERO {
-					continue;
-				}
-
-				leading[addon.0] = addon.1.clone();
-				return Some(leading);
-			},
-			_ => {},
-		}
-	}
-	None
-}
-
-*/
-
-
-/*
-fn analyze(egraph: &EGraph, _id: Id) {
-	let mut types: HashMap<Id, SpecialTerm> = HashMap::new();
-	let mut todo: VecDeque<Id> = VecDeque::new();
-	//	todo.push_back(runner.roots[0]);
-	for cls in egraph.classes() {
-		todo.push_back(cls.id);
-	}
-
-	'todo: while todo.len() > 0 {
-		let id = todo.pop_front().unwrap();
-		if types.contains_key(&id) {
-			continue 'todo;
-		}
-
-		if let Some(c) = &egraph[id].data {
-			types.insert(id, SpecialTerm::Constant(c.clone()));
-			continue 'todo;
-		}
-
-		'nodes: for n in &egraph[id].nodes {
-			match *n {
-				EquationLanguage::Unknown => {
-					types.insert(id, SpecialTerm::PowerOfX(1));
-					continue 'todo;
-				},
-				EquationLanguage::Mul([a,b]) => {
-					if !types.contains_key(&a) {
-						todo.push_back(a);
-						todo.push_back(id);
-						continue 'nodes;
-					}
-
-					if !types.contains_key(&b) {
-						todo.push_back(b);
-						todo.push_back(id);
-						continue 'nodes;
-					}
-
-					match (&types[&a], &types[&b]) {
-						(SpecialTerm::PowerOfX(dega), SpecialTerm::PowerOfX(degb)) => {
-							types.insert(id, SpecialTerm::PowerOfX(*dega + *degb));
-						},
-						(SpecialTerm::Constant(coeff), SpecialTerm::PowerOfX(deg)) => {
-							types.insert(id, SpecialTerm::Monomial(*deg, coeff.clone()));
-						},
-						_ => { continue 'nodes; },
-					}
-					continue 'todo;
-				},
-				EquationLanguage::Add([a,b]) => {
-					if !types.contains_key(&a) {
-						todo.push_front(a);
-						todo.push_back(id);
-						continue 'todo;
-					}
-
-					if !types.contains_key(&b) {
-						todo.push_front(b);
-						todo.push_back(id);
-						continue 'todo;
-					}
-
-					match (&types[&a], &types[&b]) {
-						(SpecialTerm::MonicNonconstPoly(poly), SpecialTerm::Monomial(deg, coeff)) => {
-							if poly.len() <= *deg || poly[*deg] != RATIONAL_ZERO {
-								continue 'nodes;
-							}
-
-							let mut poly = poly.clone();
-							poly[*deg] = coeff.clone();
-							types.insert(id, SpecialTerm::MonicNonconstPoly(poly));
-						},
-						_ => { continue 'nodes; },
-					}
-					continue 'todo;
-				},
-				_ => {},
-			}
-		}
-
-		types.insert(id, SpecialTerm::Other);
-	}
-
-	for (id, ty) in &types {
-		if !matches!(ty, &SpecialTerm::Other) {
-			println!("{:?}", &ty);
-		}
-	}
-}
-*/

src/output.rs

@@ -0,0 +1,66 @@
+use egg::{RecExpr, Id};
+use crate::language::EquationLanguage;
+
+// there is already a Display implementation generated by define_langauge!
+// but we want an alternative string conversion
+pub fn print_term(expr: &RecExpr<EquationLanguage>) -> String {
+	let root_id = Id::from(expr.as_ref().len()-1);
+	print_term_inner(expr, root_id).0
+}
+
+// the second result is the precedence of the top level op: 1 = '+-', 2 = '*/', 3 = '^', 4 = primitive
+fn print_term_inner(expr: &RecExpr<EquationLanguage>, id: Id) -> (String, usize) {
+	match &expr[id] {
+		EquationLanguage::Num(c) => {
+			(format!("{}", c), if c.denom == 1 { 4 } else { 2 })
+		},
+		EquationLanguage::Neg([a]) => {
+			(print_unary(expr, *a, "-", 1), 1)
+		},
+		EquationLanguage::Add([a,b]) => {
+			(print_binary(expr, *a, *b, "+", 1), 1)
+		},
+		EquationLanguage::Sub([a,b]) => {
+			(print_binary(expr, *a, *b, "-", 1), 1)
+		},
+		EquationLanguage::Mul([a,b]) => {
+			(print_binary(expr, *a, *b, "*", 2), 2)
+		},
+		EquationLanguage::Div([a,b]) => {
+			(print_binary(expr, *a, *b, "/", 2), 2)
+		},
+		EquationLanguage::Power([a,b]) => {
+			(print_binary(expr, *a, *b, "^", 3), 3)
+		},
+		_ => unimplemented!()
+	}
+}
+
+fn print_unary(expr: &RecExpr<EquationLanguage>, a: Id, op: &str, precedence: usize) -> String {
+	let (astr, aprec) = print_term_inner(expr, a);
+
+	if aprec > precedence {
+		format!("{}{}", op, astr)
+	} else {
+		format!("{}({})", op, astr)
+	}
+}
+
+fn print_binary(expr: &RecExpr<EquationLanguage>, a: Id, b: Id, op: &str, precedence: usize) -> String {
+	let (astr, aprec) = print_term_inner(expr, a);
+	let (bstr, bprec) = print_term_inner(expr, b);
+
+	if aprec > precedence {
+		if bprec > precedence {
+			format!("{} {} {}", astr, op, bstr)
+		} else {
+			format!("{} {} ({})", astr, op, bstr)
+		}
+	} else {
+		if bprec > precedence {
+			format!("({}) {} {}", astr, op, bstr)
+		} else {
+			format!("({}) {} ({})", astr, op, bstr)
+		}
+	}
+}

src/parse.rs

@@ -26,15 +26,15 @@ fn parse_equation_inner(input: &str, expr: &mut RecExpr<EquationLanguage>) -> Re
 		}
 
 		match c {
-			'^' if precedence > 3 => {
+			'^' if precedence >= 3 => {
 				operator_position = Some(i);
 				precedence = 3;
 			},
-			'*' | '/' if precedence > 2 => {
+			'*' | '/' if precedence >= 2 => {
 				operator_position = Some(i);
 				precedence = 2;
 			},
-			'-' | '+' if precedence > 1 => {
+			'-' | '+' if precedence >= 1 => {
 				operator_position = Some(i);
 				precedence = 1;
 			},