From ca621ebea5dcf4bba4d7d63dc036d84f972b461b Mon Sep 17 00:00:00 2001
From: axect <ax2ct@outlook.com>
Date: Thu, 11 Apr 2024 23:14:34 +0900
Subject: [PATCH 1/2] DEP: Add anyhow

---
 Cargo.toml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Cargo.toml b/Cargo.toml
index 567d134d..7f301446 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -37,6 +37,7 @@ lapack = { version = "0.19", optional = true }
 serde = { version = "1.0", features = ["derive"], optional = true }
 json = { version = "0.12", optional = true }
 arrow2 = { version = "0.18", features = ["io_parquet", "io_parquet_compression"], optional = true }
+anyhow = "1.0.82"
 
 [package.metadata.docs.rs]
 rustdoc-args = [ "--html-in-header", "katex-header.html", "--cfg", "docsrs"]

From 5c0657b7737684ac325d975846a766821b5d76e9 Mon Sep 17 00:00:00 2001
From: axect <ax2ct@outlook.com>
Date: Thu, 11 Apr 2024 23:17:46 +0900
Subject: [PATCH 2/2] CHGE: Change all RootFindingError to anyhow

---
 src/numerical/root.rs | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/src/numerical/root.rs b/src/numerical/root.rs
index 1462c81a..22db61c3 100644
--- a/src/numerical/root.rs
+++ b/src/numerical/root.rs
@@ -1,17 +1,7 @@
-use thiserror::Error;
-
-#[derive(Error, Debug, Clone)]
-pub enum RootFindingError {
-    #[error("No available root")]
-    NoAvailableRoot,
-    #[error("Zero derivative at {0}")]
-    ZeroDerivative(f64),
-    #[error("Constrain violated at {0}")]
-    ConstraintViolation(f64),
-}
+use anyhow::{Result, bail};
 
 pub trait RootFindingProblem<T> {
-    fn function(&self, x: f64) -> Result<f64, RootFindingError>;
+    fn function(&self, x: f64) -> Result<f64>;
     fn initial_guess(&self) -> T;
     fn derivative(&self, x: f64) -> f64 {
         unimplemented!()
@@ -22,11 +12,11 @@ pub trait RootFindingProblem<T> {
 }
 
 pub trait RootFindingMethod<T> {
-    fn step<P: RootFindingProblem<T>>(&self, problem: &P, state: T) -> Result<T, RootFindingError>;
+    fn step<P: RootFindingProblem<T>>(&self, problem: &P, state: T) -> Result<T>;
 }
 
 pub trait RootSolver {
-    fn solve<P, F, T>(&self, problem: &P, finder: &F) -> Result<f64, RootFindingError>
+    fn solve<P, F, T>(&self, problem: &P, finder: &F) -> Result<f64>
     where
         P: RootFindingProblem<T>,
         F: RootFindingMethod<T>;
@@ -45,7 +35,7 @@ impl RootFindingMethod<(f64, f64)> for BisectionMethod {
         &self,
         problem: &P,
         state: (f64, f64),
-    ) -> Result<(f64, f64), RootFindingError> {
+    ) -> Result<(f64, f64)> {
         let (a, b) = state;
         let c = (a + b) / 2.0;
 
@@ -60,7 +50,7 @@ impl RootFindingMethod<(f64, f64)> for BisectionMethod {
         } else if fc == 0.0 {
             Ok((c, c))
         } else {
-            Err(RootFindingError::NoAvailableRoot)
+            bail!("There is no root in the interval [{}, {}]", a, b);
         }
     }
 }
@@ -78,12 +68,12 @@ impl RootFindingMethod<f64> for NewtonMethod {
         &self,
         problem: &P,
         state: f64,
-    ) -> Result<f64, RootFindingError> {
+    ) -> Result<f64> {
         let f = problem.function(state)?;
         let df = problem.derivative(state);
 
         if df == 0.0 {
-            return Err(RootFindingError::ZeroDerivative(state));
+            bail!("Zero derivative at x = {}", state);
         }
 
         Ok(state - f / df)
@@ -103,15 +93,15 @@ impl RootFindingMethod<(f64, f64)> for SecantMethod {
         &self,
         problem: &P,
         state: (f64, f64),
-    ) -> Result<(f64, f64), RootFindingError> {
+    ) -> Result<(f64, f64)> {
         let (x0, x1) = state;
         let f0 = problem.function(x0)?;
         let f1 = problem.function(x1)?;
 
         if f0 == f1 {
-            return Err(RootFindingError::ZeroDerivative(x0));
+            bail!("Zero secant at ({}, {})", x0, x1);
         }
 
-        unimplemented!()
+        Ok((x1, x1 - f1 * (x1 - x0) / (f1 - f0)))
     }
 }