How to resolve the algorithm Determine if a string is numeric step by step in the Clojure programming language

Published on 12 May 2024 09:40 PM
#Clojure

How to resolve the algorithm Determine if a string is numeric step by step in the Clojure programming language

Table of Contents

Problem Statement

Create a boolean function which takes in a string and tells whether it is a numeric string (floating point and negative numbers included) in the syntax the language uses for numeric literals or numbers converted from strings.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Determine if a string is numeric step by step in the Clojure programming language

Source code in the clojure programming language

(defn numeric? [s]
  (if-let [s (seq s)]
    (let [s (if (= (first s) \-) (next s) s)
          s (drop-while #(Character/isDigit %) s)
          s (if (= (first s) \.) (next s) s)
          s (drop-while #(Character/isDigit %) s)]
      (empty? s))))


(numeric? [\1 \2 \3])  ;; yields logical true


(require '[clojure.edn :as edn])
(import [java.io PushbackReader StringReader])

(defn number-string? [s]
  (boolean
    (when (and (string? s) (re-matches #"^[+-]?\d.*" s))
      (let [reader (PushbackReader. (StringReader. s))
            num (try (edn/read reader) (catch Exception _ nil))]
        (when num
          ; Check that the string has nothing after the number
          (= -1 (.read reader)))))))


user=> (number-string? "2r101010")
true
user=> (number-string? "22/7")
true

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