Constant values

[timothee-haudebourg]

I propose to add a new construct in TreeLDR: constants. A constant is a named construct, just like a layout, struct field, or enum variant that holds a value formatted with a given layout.

The general syntax is:

const Name: Layout = Value ;

For instance:

const PI: xs:decimal = 3.1415;

This will require implementing value expressions.

Such a constant can then be exported in the target language as a constant definition. For instance in Rust:

const PI: f64 = 3.1415;