Macro expr_as 

macro_rules! expr_as {
    ($t:ty, $template:expr) => { ... };
    ($t:ty, $template:expr, $($param:tt),*) => { ... };
}

Macro to create expressions with template and parameters for any type T Syntax:

• expr_as!(T, “template”, arg) -> arg becomes Scalar
• expr_as!(T, “template”, (expr)) -> expr becomes Nested
• expr_as!(T, “template”, {deferred}) -> deferred becomes Deferred