Delimited Continuations
If you’ve programmed in an imperative language, chances are you’ve used a guard clause to return early from a method or function in certain cases, like the following Ruby code that approximates following someone on Twitter:
| control_flow/guard_clause.rb | |
| | def follow_user(user, user_to_follow) |
| | if user_to_follow.blocked?(user) |
| | puts "#{user_to_follow.name} has blocked #{user.name}" |
| | return |
| | end |
| | user.following << user_to_follow |
| | user_to_follow.followers << user |
| | end |
Early returns can be confusing if we use them all over the place, but they can be useful to describe requirements for the main method body to execute. Normally in Clojure, we’d need to write something like this:
| control_flow/guard_clause_1.clj ... |
Get Mastering Clojure Macros now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
