[EdwardCoffin]

I have the same Meeus book. It's been a while since I read it, but my impression was the signs of longitudes being turned around was not unique to his book, but was rather a convention throughout astronomy, so you could expect to find whatever other books you're recommended would have the same convention.

When I was contemplating my own implementation from that book my sketchy API design just included a mandatory extra parameter to accompany such numbers, which would explicitly indicate whether the astronomical or other sign convention was to be used.

[AlphaGeekZulu]

You are right. As I have come to understand, there is a difference in astronomic longitudes and geographic longitudes as they are used for navigation.

The extra parameter is a good idea. As I am implementing in Rust, I will follow the strong type system and provide two different types that can cast themselves into the other.