Replace a few substrings in Scala

Question

Suppose I need to replace few patterns in a string :

val rules = Map("abc" -> "123", "d" -> "4", "efg" -> "5"} // string to string
def replace(input:String, rules: Map[String, String] = {...}

replace("xyz", rules)       // returns xyz
replace("abc123", rules)    // returns 123123
replace("dddxyzefg", rules) // returns 444xyz5

How would you implement replace in Scala ? How would you generalize the solution for rules : Map[Regex, String] ?

Randall Schulz · Accepted Answer · 2014-03-28 16:56:17Z

5

It's probably easier just to go straight to the general case:

val replacements = Map("abc".r -> "123", "d".r -> "4", "efg".r -> "5")

val original = "I know my abc's AND my d's AND my efg's!"

val replaced = replacements.foldLeft(original) { (s, r) => r._1.replaceAllIn(s, r._2) }
replaced: String = I know my 123's AND my 4's AND my 5's!

answered Mar 28, 2014 at 16:56

Randall Schulz

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2 Comments

Michael Over a year ago

Ok, thanks. Looks like looping over all replacements and call replaceAllfor each of them. Is it optimal performance/complexity-wise?

Randall Schulz Over a year ago

I don't think there's a straightforward alternative. If all the replacement targets had the same replacement string, you could combine the target patterns with the | regex operator and do a single replaceAllIn. Otherwise, there's nothing simple I can think of. But unless you have gobs of replacemens in your Map or the multi-replace will happen in an "inner loop," the performance probably won't be a problem.

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