lstrip and rstrip non blank character from string

Question

How do you strip characters (not necessarily white space i.e. blanks) from the start and end of a String in Scala?

The Python analogue to what I am looking for is lstrip and rstrip.

This is the desired functionality:

ltrim("{blah blah}", "{") should equal("blah blah}")
ltrim("blah blah", "{") should equal("blah blah") // no exception

rtrim("blah blah}", "}") should equal("blah blah")

Answer 1

You could use dropWhile if you want to remove a specific character from the beginning of a String:

"{{blah blah}".dropWhile(_ == '{')
// "blah blah}"

This drops any character from the left of the String which fulfills the given predicate which in this case is being equal to the character to remove.

---

In order to remove a character from the right, since there is not yet a dropWhileRight equivalent in the standard library, one way could consist in a double reverse:

"{{blah blah}".reverse.dropWhile(_ == '}').reverse
// {{blah blah

or slightly more efficients:

"{{blah blah}}".dropRight("{{blah blah}}".reverse.segmentLength(_ == '}'))
// {{blah blah
"{{blah blah}}".stripSuffix("{{blah blah}}".reverse.takeWhile(_ == '}'))
// {{blah blah

Answer 2

Use regular expressions functions

scala> "{blah blah}".replaceAll("""^[{]+""","")
res35: String = blah blah}

scala> "{{blah blah}".replaceAll("""^[{]+""","")
res36: String = blah blah}

scala> "blah blah}".replaceAll("""^[{]+""","")
res37: String = blah blah}

scala> "blah blah}".replaceAll("""[}]+$""","")
res38: String = blah blah

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