pub fn as_f64(e: &Expr) -> f64 {
    match *e {
        Expr::Approx(f) => f,
        _ => panic!("{} is not a float", e),
    }
}
/// A helper function to convert `Expr` to f64.
A helper function to convert `Expr` to f64.
A helper function to convert ` Expr ` to f64 .
pub fn as_f64(e: &Expr) -> f64 {
    match *e {
        Expr::Approx(f) => f,
        _ => panic!("{} is not a float", e),
    }
}
pub fn as_f64 ( e : & Expr ) -> f64 { match * e { Expr :: Approx ( f ) => f , _ => panic ! ( " " e ) , } }
A helper function to convert `Expr` to f64.
A helper function to convert ` Expr ` to f64 .
e
&Expr