Function eval 

pub fn eval(
    expr: &str,
    var_names: &[&str],
    vars: &[f64],
) -> Result<f64, EvalError>

Convenience function to parse, compile, and evaluate in one call.

This is useful for one-off evaluations where you don’t need to reuse the compiled expression.

Arguments

• expr - The expression string
• var_names - Variable names
• vars - Variable values

Example

use mathexpr::eval;

let result = eval("x + y", &["x", "y"], &[3.0, 4.0])?;
assert_eq!(result, 7.0);