Macro develop_debug::develop_debug

macro_rules! develop_debug {
    (output true) => { ... };
    (output false) => { ... };
    (title $(,)? $fmt:literal $(,)? $($msg:expr),*) => { ... };
    (step $(,)? $fmt:literal $(,)? $($msg:expr),*) => { ... };
    (var $(,)? $($arg:expr),*) => { ... };
    (iter $(,)? $($arg:expr),*) => { ... };
    (done $(,)? $fmt:literal $(,)? $($msg:expr),*) => { ... };
    (error $(,)? $fmt:literal $(,)? $($msg:expr),*) => { ... };
    ($($args:tt)*) => { ... };
}

Print debugging information at development time.

See the manual