Expand description
std::concat! with support for const variables and expressions.
Works on stable Rust ✨.
§🚀 Getting started
Add constcat to your Cargo manifest.
cargo add constcat
Import the macro using the following.
use constcat::concat;§🤸 Usage
§String slices
concat! works exactly like std::concat!, concatenating &str
literals into a static string slice, except you can now pass variables and
constant expressions.
const CRATE_NAME: &str = env!("CARGO_PKG_NAME");
const CRATE_VERSION: &str = env!("CARGO_PKG_VERSION");
const fn tada() -> &'static str { "🎉" }
const VERSION: &str = concat!(CRATE_NAME, " ", CRATE_VERSION, tada());§Byte slices
concat_bytes! works similarly to concat!, concatenating const
&[u8] expressions and literals into a static byte slice.
const VERSION: u32 = 1;
const fn entries() -> &'static [u8] { b"example" }
const HEADER: &[u8] = concat_bytes!(&VERSION.to_le_bytes(), entries());§T slices
concat_slices! is the underlying macro used for both of the above, this
can be used to concatenate const &[T] expressions into a static
slice.
This macro requires the type of slice to be specified in the form [T]:
before the comma separated expressions.
const MAGIC: &[i32; 4] = &[1, 3, 3, 7];
const VERSION: i32 = 1;
const HEADER: &[i32] = concat_slices!([i32]: MAGIC, &[0, VERSION]);const PRIMARIES: &'static [(u8, u8, u8)] = &[(255, 0, 0), (0, 255, 0), (0, 0, 255)];
const SECONDARIES: &'static [(u8, u8, u8)] = &[(255, 255, 0), (255, 0, 255), (0, 255, 255)];
const COLORS: &[(u8, u8, u8)] = concat_slices!([(u8, u8, u8)]: PRIMARIES, SECONDARIES);