feat: add thiserror for a real error impl

Cargo.toml

@@ -24,6 +24,7 @@ integraal = { version = "0.0.4", path = "./integraal" }
 integraal-examples = { version = "0.0.4", path = "./examples" }
 
 # external
+num-traits = "0.2.19"
 rand = "0.9.0-alpha.2"
 rustversion = "1.0.15"
-num-traits = "0.2.19"
+thiserror = "1.0.64"

integraal/Cargo.toml

@@ -24,6 +24,7 @@ romberg = []              # gated because it is not implemented for all input ki
 [dependencies]
 num-traits.workspace = true
 rand = { workspace = true, features = ["small_rng"], optional = true }
+thiserror.workspace = true
 
 [build-dependencies]
 rustversion.workspace = true

integraal/src/structure/definitions.rs

@@ -7,15 +7,19 @@ use crate::{ComputeMethod, DomainDescriptor, FunctionDescriptor, Scalar};
 // ------ CONTENT
 
 /// Integral error
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, thiserror::Error)]
 pub enum IntegraalError {
     /// Some parameters do not fit the requirements of the computation method.
+    #[error("{0}")]
     BadParameters(&'static str),
     /// Specified parameters are conflicting or ambiguous.
+    #[error("{0}")]
     InconsistentParameters(&'static str),
     /// One or more parameters are missing.
+    #[error("{0}")]
     MissingParameters(&'static str),
     /// A given method isn't implemented for the specified parameters (e.g. due to requirements).
+    #[error("{0}")]
     Unimplemented(&'static str),
 }
 

integraal/src/structure/implementations.rs

@@ -42,8 +42,8 @@ impl<'a, X: Scalar> Integraal<'a, X> {
     /// - `Ok(X: Scalar)` -- The computation was successfuly done
     /// - `Err(IntegraalError)` -- The computation failed for the reason specified by the enum.
     pub fn compute(&mut self) -> Result<X, IntegraalError> {
-        // ensure all data is defined
-        if self.domain.is_none() | self.function.is_none() | self.method.is_none() {
+        // ensure all data is defined; evaluate function first because it is reset after all computations
+        if self.function.is_none() | self.domain.is_none() | self.method.is_none() {
             return Err(IntegraalError::MissingParameters(
                 "one or more parameter is missing",
             ));