Clojure stripMargin

Question

Scala offers a method called stripMargin that removes the left-hand part of a multiline string up to a specified delimiter (default: "|"). Here is an example:

"""|Foo
   |Bar""".stripMargin

returns the string

Foo
Bar

Is there a similar function in Clojure? If not, how would you implement it (most functionally)?

Thanks.

UPDATE: The example I gave is not complete. The stripMargin method also preserves whitespace after the delimiter:

"""|Foo
   |   Bar""".stripMargin

returns the string

Foo
   Bar

Answer 1

A quick googling didn't return any existing functions, but here is my attempt at the problem. It doesn't support custom delimiters and it is not very optimized speedwise.

(use '[clojure.contrib.str-utils :only (re-split re-sub str-join)])

(defn strip-margin [s]
  (let [lines (seq (re-split #"\n" s))]
    (str-join "\n"
      (for [line lines]
        (re-sub #"^\s*\|" "" line)))))

Answer 2

There is no such function built in but you write it easily:

user=> (use '[clojure.contrib.string :only (join, split-lines, ltrim)]) //'
nil
user=> (->> "|Foo\n  |Bar" split-lines (map ltrim) 
  (map #(.replaceFirst % "\\|" "")) (join "\n"))
"Foo\nBar"

Answer 3

Here my complete solution, gathered from the answers above:

(use '[clojure.contrib.string :only (join, split-lines, ltrim)])

(defn strip-margin
  ([s d] (->> s split-lines (map ltrim) (map #(.replaceFirst % d "")) (join "\n")))
  ([s] (strip-margin s "\\|")))

Here is some "real" sample input and output:

(println
  (strip-margin "|<?xml version='1.0' encoding='utf-8'?>
                 |<people>
                 |  <person>
                 |    <name>Joe Smith</name>
                 |  </person>
                 |</people>"))

==>

<?xml version='1.0' encoding='utf-8'?>
<people>
  <person>
    <name>Joe Smith</name>
  </person>
</people>
nil

Thanks to all contributors.

Answer 4

You can also do this with a single regexp:

(use '[clojure.contrib.string :only (replace-re)])

(def test-string 
"|<?xml version='1.0' encoding='utf-8'?>
                 |<people>
                 |  <person>
                 |    <name>Joe Smith</name>
                 |  </person>
                 |</people>")


(replace-re #"(^\|)|(.+\|)" "" test-string))