February 2018
Intermediate to advanced
304 pages
7h 11m
English
Content preview from Programming Clojure, 3rd Edition
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Creating Ad Hoc Taxonomies
Multimethods let you create ad hoc taxonomies, which can be helpful when you discover type relationships that are not explicitly declared as such.
For example, consider a financial application that deals with checking and savings accounts. Define a Clojure map for an account, using a tag to distinguish the two:
| | (ns examples.multimethods.account) |
Now, you’re going to create two different checking accounts, tagged as ::checking and ::savings. The doubled :: causes the keywords to resolve in the current namespace. To see the namespace resolution happen, compare entering :checking and ::checking at the REPL:
| | :checking |
| | -> :checking |
| | |
| | ::checking |
| | -> :user/checking |
Placing keywords ...
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