Clojure string/replace fails in my function

Question

I want to replace space characters with plus signs in the search query I send to google.

(defn search-google [search-term]
  (clojure.string/replace search-term #" " "+")
    (browse-url 
      (str "http://google.ca/search?q=" search-term)))

However my function fails as my search-term retains spaces.

(search-google "clojure user input")

URISyntaxException Illegal character in query at index 32:
http://google.ca/search?q=clojure user input  java.net.URI$Parser.fail (:-1)

I am new at clojure and suspect I am missing something obvious.

Arthur Ulfeldt · Accepted Answer · 2013-02-19 23:41:58Z

3

A new fixed search-term is being created, then the fixed one is ignored and the unchanged one is passed to browse-url:

(def browse-url println)                                                                                                                                                  
(defn search-google [search-term]                                                                                                                                         
  (let [fixed-search-term (clojure.string/replace search-term #" " "+")]                                                                                                  
    (browse-url                                                                                                                                                           
     (str "http://google.ca/search?q=" fixed-search-term))))  

user> (search-google "a b c")                                                                                                                                             
http://google.ca/search?q=a+b+c                                                                                                                                           
nil

answered Feb 19, 2013 at 23:41

Arthur Ulfeldt

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1 Comment

exbctel Over a year ago

Thanks Arthur and @andrewdotnich for the explanation about let.

Óscar López · Accepted Answer · 2013-02-19 23:43:37Z

2

Try this instead:

(defn search-google [search-term]
  (browse-url 
   (str "http://google.ca/search?q="
        (clojure.string/replace search-term #"\s+" "+"))))

Notice that the pattern is a regular expression, and you can use \s+ to indicate that the string match to be replaced should include one or more spaces.

Also be aware that the replace procedure returns a new string, the original string is not modified.

edited Feb 19, 2013 at 23:43

answered Feb 19, 2013 at 23:38

Óscar López

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4 Comments

exbctel Over a year ago

Sorry, that didn't work. Maybe I have to re-bind search-term to it's new value. In python it would be search_term = search_term.replace(' ','+')

Óscar López Over a year ago

@exbctel no need to do that, the string is correctly formed before being passed as a parameter, to see it try this: (str "http://google.ca/search?q=" (clojure.string/replace "a b c d" #"\s+" "+")) maybe there are other erroneous characters in the search term?

exbctel Over a year ago

Thanks Oscar. Moving the string/replace into browse-url worked. However I ended up using the let re-binding suggested by Arthur and Andrew instead.

Óscar López Over a year ago

@exbctel you're welcome! remember that let is useful, but not required to make the code work - you can pass the value directly, as shown above. Also be aware that the other answers don't take in consideration the case where there are more than one spaces in-between

andrewdotnich · Accepted Answer · 2013-02-19 23:41:55Z

1

Replace doesn't modify search-term in-place, but rather returns a copy of it, which is being thrown away.

Use let to bind this value to a name in the function and call browse-url with that instead.

answered Feb 19, 2013 at 23:41

andrewdotnich

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