A procedural macro to generate a closure that checks if a character is in the provided literal string.
cargo add in_struse in_str::in_str;
let _ = in_str!("abc");
// equals to
let _ = |c: char| matches!(c, 'a' | 'b' | 'c');
// usually faster than
let _ = |c: char| "abc".contains(c);
// escape will be handled automatically
let _ = in_str!("\n\u{10ffff}");
// equals to
let _ = |c: char| matches!(c, '\n' | '\u{10ffff}');
// also works with byte strings
let _ = in_str!(b"abc");
// equals to
let _ = |c: u8| matches!(c, b'a' | b'b' | b'c');
// escape will be handled automatically
let _ = in_str!(b"\n\xff");
// equals to
let _ = |c: u8| matches!(c, b'\n' | 0xff);