REPL Experiments with Clojure Spec

Create a minimal Project

Clojure Spec can be tried without creating a Clojure project, although creating a project is useful if saving the Clojure Spec code experiments.

Create a minimal Clojure project with a Clojure CLI deps.edn configuration.

clojure -T:project/create :template practicalli/minimal :name practicalli/spec-experiments

Run a Clojure REPL with a rich terminal UI

REPL RebelREPL Reloaded

A REPL with a rich terminal UI

clojure -M:repl/rebel

A REPL with a rich terminal UI and tools to support the Practicalli REPL Reloaded workflow.

clojure -M:repl/reloaded

Require the clojure.spec.alpha using an alias called spec to use functions from that namespace.

(require '[clojure.spec.alpha :as spec])

NOTE: clojure.spec.alpha is often aliased as s, although Practicalli avoids

Spec auto-completion

Using rebel-readline for the Clojure REPL will show autocompletion for all spec functions once the spec namespace has been required.

Type (spec / and press TAB to list all the functions in the namespace.

Typing a space character after the full name of a function shows the function signature with arguments that should be passed to that function.

Ctrl x Ctrl d displays the documentation for the current function

Check data conforms to specification

Use the spec/conform and spec/valid? functions to test if data matches a specification. In these examples, predicate functions are used as a specification.

Example expressions

spec/conform will return the value if it conforms to the specification, or :clojure.spec.alpha/invalid if the data does not conform.

Clojure Spec - Conform values

(spec/conform odd? 101)

(spec/conform integer? 1)

(spec/conform seq? [1 2 3])

(spec/conform seq? (range 10))

(spec/conform map? {})

(spec/conform map? (hash-map :a 1 :b 2))

spec/valid? returns true or false

Clojure Spec - validate values

(spec/valid? even? 180)

(spec/valid? string? "Am I a valid string")

(spec/valid? (fn [value] (> value 10000)) 30076)

(spec/valid? #(> % 10000) 30076)

(spec/conform #(> % 10000) 30076)