Function eval_function 

pub fn eval_function(
    name: &str,
    params: &[Param],
    body: &Expr,
    current_env: &HashMap<String, Value>,
    env_set: impl FnMut(String, Value),
) -> Result<Value, InterpreterError>

Evaluate a function definition

Complexity

Cyclomatic complexity: 3 (within Toyota Way limits)