How to write a parser algorithm?

Question

Parsing

Good afternoon, dear reader!
How to write a parser algorithm? Based on weather data, I want to make a notification based on the Telegram bot that, is it possible to look at the Moon through a telescope tonight?
In general, how are algorithms developed?
Thanks for answers!

Answer 1

The algorithm is developed very simply:

1. First, they develop a TOR - a technical task with a description of what and how it is and how it should be, as well as with all the requirements
   
2. Next, the task is decomposed into smaller tasks.
   
3. Then, all the small details are worked out and analyzed in more detail.
   
4. As a result, we get Private / full TK
   
5. Based on this TOR, the logic and all parts of the software / Algorithm are already being implemented
   

Answer 2

Dmitry Soshnikov gives an example of parsers in a course on functional programming (he claims that it is the functional approach that makes it easy to write parsers).
There are also two sections on parsers in the "Haskell, part 2" course on Stepika in the applicative functors section. But it is added there that it is desirable to do grammar and run a lexer before the parser (no examples), which parses the input stream into tags (and those are already parsed by the parser). So you can study what grammar, vocabulary, syntax, etc. are.