Common Functions and Macros

This section is the “you’ll use these daily” list: core functions and macros that show up in almost every Clojure codebase.

If you are translating Java loops, focus on the sequence toolbox (map, filter, reduce) and on threading macros (->, ->>) that make transformation pipelines easy to read.

In this section

• Sequence Operations
  Use map/filter/reduce and friends to build readable data pipelines; most sequence transforms are lazy.
• Collection Manipulation
  The everyday update operations for persistent collections: get/assoc/update/conj plus dissoc/disj/into and nested helpers.
• Function Composition and Utilities
  Build functions from functions with comp/partial/juxt plus apply and memoize for practical pipelines.
• Threading Macros
  Make transformation pipelines readable with ->, ->>, and the conditional threading variants some-> and cond->.
• Conditional Macros
  Everyday branching tools beyond if: when, if-let/when-let, cond, and case (plus the truthiness rules that matter).