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use super::*; use calculator::Calculator; use evaluator::{Evaluator, Function}; use parser::{Parser, Operator, OperatorAssociativity}; use tokenizer::Tokenizer; use polynomial_calculator::{PolynomialParser, PolynomialEvaluator}; use polynomial::Polynomial; #[derive(Debug, PartialEq)] pub enum SolvingError { NonLinear, NoSymbol, Tautology, NonSolvable } pub struct LinearSolver; impl Calculator<Tokenizer, LinearSolverParser, LinearSolverEvaluator> for LinearSolver { } pub struct LinearSolverEvaluator { pub evaluator: Evaluator } impl Default for LinearSolverEvaluator { fn default() -> LinearSolverEvaluator { let mut evaluator = PolynomialEvaluator::default().evaluator; evaluator.register_function("=", Function::new(2, Box::new(functions::solver))).unwrap(); LinearSolverEvaluator { evaluator: evaluator } } } impl TokensReducer for LinearSolverEvaluator { fn process(&self, tokens: &Tokens) -> Result<Polynomial, EvaluationError> { self.evaluator.process(tokens) } } pub struct LinearSolverParser { pub parser: Parser } use std::i64; impl Default for LinearSolverParser { fn default() -> LinearSolverParser { let mut parser = PolynomialParser::default().parser; parser.register_operator('=', Operator::new(i64::MIN, OperatorAssociativity::Left)); LinearSolverParser { parser: parser } } } impl TokensProcessor for LinearSolverParser { fn process(&mut self, tokens: &Tokens) -> Result<&Tokens, ParsingError> { self.parser.process(tokens) } } mod functions { use super::*; use polynomial::Polynomial; use EvaluationError; pub fn solver(mut args: Vec<Polynomial>) -> Result<Polynomial, EvaluationError> { let mut right = args.pop().unwrap(); let mut left = args.pop().unwrap(); let right_degree = right.degree(); let left_degree = left.degree(); if left_degree > 1 || right_degree > 1 { Err(EvaluationError::SolvingError(SolvingError::NonLinear)) } else if left_degree == 0 && right_degree == 0 { Err(EvaluationError::SolvingError(SolvingError::NoSymbol)) } else { if right_degree > 0 { left[1] -= right[1]; right[1] -= right[1]; } right[0] -= left[0]; left[0] -= left[0]; right[0] /= left[1]; left[1] /= left[1]; if right[0].is_nan() { Err(EvaluationError::SolvingError(SolvingError::Tautology)) } else if right[0].is_infinite() { Err(EvaluationError::SolvingError(SolvingError::NonSolvable)) } else { Ok(right) } } } } #[cfg(test)] mod tests { use super::*; use EvaluationError; use polynomial::Polynomial; use calculator::{Calculator, CalculationError}; #[test] fn test_general() { assert_eq!(LinearSolver.process("2 * x + 0.5 = 1"), Ok(Polynomial::constant(0.25))); assert_eq!(LinearSolver.process("2x + 1 = 2(1-x)"), Ok(Polynomial::constant(0.25))); assert_eq!(LinearSolver.process("x^2-x^2+x=2"), Ok(Polynomial::constant(2.0))); assert_eq!(LinearSolver.process("1-x=x"), Ok(Polynomial::constant(0.5))); } #[test] fn test_position_agnostic() { assert_eq!(LinearSolver.process("x=2"), Ok(Polynomial::constant(2.0))); assert_eq!(LinearSolver.process("2=x"), Ok(Polynomial::constant(2.0))); assert_eq!(LinearSolver.process("x-2=0"), Ok(Polynomial::constant(2.0))); assert_eq!(LinearSolver.process("0=-2+x"), Ok(Polynomial::constant(2.0))); } #[test] fn test_restrictions() { assert_eq!(LinearSolver.process("x^2=5"), Err(CalculationError::EvaluationError(EvaluationError::SolvingError(SolvingError::NonLinear)))); assert_eq!(LinearSolver.process("2=2"), Err(CalculationError::EvaluationError(EvaluationError::SolvingError(SolvingError::NoSymbol)))); } #[test] fn test_special_cases() { assert_eq!(LinearSolver.process("x=x"), Err(CalculationError::EvaluationError(EvaluationError::SolvingError(SolvingError::Tautology)))); assert_eq!(LinearSolver.process("x=x+1"), Err(CalculationError::EvaluationError(EvaluationError::SolvingError(SolvingError::NonSolvable)))); } }