Enum EvalError 

pub enum EvalError {
    UndefinedSymbol(String),
    DivisionByZero,
    DomainError(String),
    NaN(String),
    MaxRecursionDepthExceeded(usize),
}

Errors that can occur during the numerical evaluation of symbolic parameters.

This enum captures failure modes when resolving a symbolic Parameter expression into a concrete floating-point value. These errors typically arise while binding a parameterized quantum circuit.

Variants

UndefinedSymbol(String)

Indicates that a symbolic variable required for evaluation was missing from the provided bindings.

Example

evaluating theta + phi with bindings { "theta": 1.0 } will raise UndefinedSymbol("phi").

DivisionByZero

Indicates an arithmetic error where a division or modulo operation by zero occurred.

This includes both explicit division by zero (e.g., x / 0.0) and runtime zeros (e.g., x / y where y = 0.0).

DomainError(String)

Indicates that a mathematical function was called with an argument outside its defined domain.

Common causes include:

• sqrt(x) where x < 0
• ln(x) where x <= 0
• asin(x) or acos(x) where |x| > 1

NaN(String)

Indicates that an intermediate or final calculation resulted in NaN (Not a Number).

This serves as a catch-all for undefined numerical behaviors not covered by other variants.

MaxRecursionDepthExceeded(usize)

Indicates that the expression tree exceeded the maximum allowed recursion depth during evaluation.

This typically occurs with deeply nested expressions (e.g., ((((x+1)+1)+1)...)). Consider simplifying the expression or increasing the depth limit.

Trait Implementations

impl Debug for EvalError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for EvalError

fn fmt(&self, __formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for EvalError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<EvalError> for CircuitError

fn from(source: EvalError) -> Self

Converts to this type from the input type.