How deeply does Clojure: The Essential Reference cover sort-by?

Defines arities, input contracts, sortable values, outputs, and comparison exceptions without detailing the sorting algorithm.

Sort-by

As explained in Clojure: The Essential Reference

sort-by is a Clojure function that orders collection elements according to comparator results computed from a key function.

sort-by orders a collection by applying a one-argument key function to each element, then comparing the resulting keys. It uses compare by default or accepts an explicit comparator, returning an ordered sequence. section 8.3.5

Sorting by a map key

(sort-by :age [{:age 65} {:age 13} {:age 8}]) ;; ({:age 8} {:age 13} {:age 65}) The key function can also transform values before comparison: (sort-by str [:f "s" \c 'u]) orders unlike values by their string representations.

Use the contract to choose inputs and comparators:

Pass a collection supported by seq; transients and scalars are rejected. section 8.3.5
Ensure elements or computed keys are mutually sortable, or ClassCastException may result. section 8.3.5

How Clojure: The Essential Reference covers it

Cover of Clojure: The Essential Reference

liveBook manning.com

Read Clojure: The Essential Reference on liveBook Get the book at manning.com

Related concepts

comparison functionuses · A comparison function or strategy compares two values and indicates their relative ordering, and sometimes whether they are equivalent.
comparison predicateused by · A predicate that evaluates an ordering relationship among one or more values and returns a Boolean result.
sorted-set-byalternative to · sorted-set-by is a Clojure constructor function that creates a sorted set using a supplied comparator.

This explainer was generated by Manning's knowledge graph from the text of Clojure: The Essential Reference. The section links point to the parts of the book it draws on.