Add count

[pzp1997]

count is a simple but useful function for checking how many things in a list satisfy some predicate. It is great for when you don't care about the particulars of those things but only their quantity. An example of a good real-world use case is if you are accepting text input from the user and you want to know how many of the words/sentences they used have a particular property.

Suppose we give our students an activity to make complex sentences. A parameter that we might use to check a sentence is seeing if it contains more than one clause, which we can approximate by checking if it contains a , character and is adequately long. In order to determine if a student is successful, we simply want to know how many of their sentences satisfy our complexity rule. We can easily do this using count!

[Chadtech]

Cool, that all makes sense to me.