Macro trace 

macro_rules! trace {
    (logger: $logger:expr, target: $target:expr, $($arg:tt)+) => { ... };
    (logger: $logger:expr, $($arg:tt)+) => { ... };
    (target: $target:expr, $($arg:tt)+) => { ... };
    ($($arg:tt)+) => { ... };
}

Logging (docs/logging.md). day::info!("…") and friends are the log crate’s macros, re-exported so an app needs no log dependency of its own for the common case. Because they are log’s, anything that speaks log (env_logger, tracing-log, a hand-written log::Log) works without adapters.

Day installs a default logger at launch, so these come out with no setup on every platform: stderr natively, the browser console on web-dom. An app that wants something else calls log::set_logger (or env_logger::init()) before day::launch and keeps it. Logs a message at the trace level.

Examples

use log::trace;

let pos = Position { x: 3.234, y: -1.223 };

trace!("Position is: x: {}, y: {}", pos.x, pos.y);
trace!(target: "app_events", "x is {} and y is {}",
       if pos.x >= 0.0 { "positive" } else { "negative" },
       if pos.y >= 0.0 { "positive" } else { "negative" });
trace!(logger: my_logger, "x is {} and y is {}",
       if pos.x >= 0.0 { "positive" } else { "negative" },
       if pos.y >= 0.0 { "positive" } else { "negative" });