Rust

Certain regexes that are used with Regex::new or RegexBuilder::new may be replaced by common str methods, such as str::starts_with, str::ends_with, str::contains and str::cmp.

Calls to expect followed by a function call should be replaced with unwrap_or_else to increase laziness. The argument to expect is evaluated eagerly and unconditionally. The argument to unwrap_or_else is evaluated lazily and only if required, sometimes leading to lower overhead and fewer allocations.

Calls to unwrap_or followed by a function call should be replaced with unwrap_or_else or unwrap_or_default, to increase laziness. The argument to unwrap_or is evaluated eagerly and unconditionally. unwrap_or_else or unwrap_or_default are evaluated lazily and only if required, sometimes leading to lower overhead and fewer allocations.

.bytes().nth(..) is better written as .as_bytes().get(..) which is more performant.

These busy loops burn CPU cycles without doing anything. It is almost always a better idea to panic! than to have a busy loop.