Println! and eprintln

Println!

The first tool which you may reach for when you experience unexpected behaviour is println!. println! can be used, as the name suggests, to print values at key points of your program where your issue might lie.

However

• Typing, or more likely copying and pasting println!'s everywhere gets quite tedious.
• Each println! should, in most cases, have some marking string that lets you know which one triggered, otherwise you have to do additional searching.
• At some point, these println!'s need to be removed, or they will block up the logging.