412 PurelyFunctional.tv Newsletter

00 Valid names.md

Valid names

This challenge looks like a fun experiment in building a simple rules-based validator.

Definitions:

1. A name is a sequence of terms separated by a space. It must have at least 2 terms. The last term must be a word.
2. A term is either an initial or a word.
3. An initial is a single capital letter followed by a period.
4. A word is a capital letter followed by one or more letters (upper or lower case).

Write a function that checks whether a string is a valid name.

Examples

Valid names:

• George R. R. Martin
• Abraham Lincoln
• J. R. Bob Dobbs
• H. G. Wells

Invalid names:

• J R Tolkien (no periods)
• J. F. K. (must end in word)
• Franklin (must have at least two terms)

Thanks to this site for the challenge idea where it is considered Expert in JavaScript. The problem has been modified from the original.

Please submit your solutions as comments on this gist.

@andyfry01 Yes, I thought spec can be used nicely for this kind of problem!

@pieterbreed you're too kind; in the real world I would absolutely use a solution closer to yours than the one I posted. Regexes are awesome! 😉

Spec really is shining in this one wow

(ns pftv.challenges.412
  (:require [clojure.spec.alpha :as spec]
            [clojure.string :as str]))

(spec/def ::initial (partial re-matches #"[A-Z]\."))

(spec/def ::word (partial re-matches #"[A-Z][A-Za-z]+"))

(spec/def ::term (spec/or :initial ::initial :word ::word))

(spec/def ::name (spec/cat
                  :terms (spec/+ ::term)
                  :ends-in-word ::word))

(defn valid-name? [name]
  (let [name-vec (str/split name #" ")]
    (spec/valid? ::name name-vec)))

(def valid-names ["George R. R. Martin"
                  "Abraham Lincoln"
                   "J. R. Bob Dobbs"
                  "H. G. Wells"])

(def invalid-names ["J R Tolkien"
                      "J. F. K."
                      "Franklin"])
(every? true?
        (map valid-name? valid-names))
;; => true

(every? false?
        (map valid-name? invalid-names))
;; => true