What are the benefits of applicative parsing over monadic parsing?

Question

There seems to be a consensus that you should use Parsec as an applicative rather than a monad. What are the benefits of applicative parsing over monadic parsing?

Answer 1

The main reason I can see to prefer applicative parsers over monadic parsers is the same as the main reason to prefer applicative code over monadic code in any context: being less powerful, applicatives are simpler to use.

This is an instance of a more general engineering dictum: use the simplest tool which gets the job done. Don't use a fork lift when a dolly will do. Don't use a table saw to cut out coupons. Don't write code in IO when it could be pure. Keep it simple.

But sometimes, you need the extra power of Monad. A sure sign of this is when you need to change the course of the computation based on what has been computed so far. In parsing terms, this means determining how to parse what comes next based on what has been parsed so far; in other words you can construct context-sensitive grammars this way.