Domain Specific Languages (DSLs)
A DSL is a mini "language" embedded in a Rust macro. It is completely valid Rust because the macro system expands into normal Rust constructs, but it looks like a small language. This allows you to define concise or intuitive syntax for some special functionality (within bounds).
Suppose that I want to define a little calculator API. I would like to supply an expression and have the output printed to console.
Output:
1 + 2 = 3
(1 + 2) * (3 / 4) = 0
This was a very simple example, but much more complex interfaces have been
developed, such as lazy_static
or
clap
.
Also, note the two pairs of braces in the macro. The outer ones are
part of the syntax of macro_rules!
, in addition to ()
or []
.