Merge the intersection of two CSV files with Scala

Question

From input 1:

fruit, apple, cider  
animal, beef, burger

and input 2:

animal, beef, 5kg
fruit, apple, 2liter
fish, tuna,          


        

Answer 1

It's tough to infer a requirement from one example. May be something like this is would serve your needs:

• Create a map from key to line for the second file f2 (so from "animal, beef" -> "5kg")
• For each lines in the first file f1, get the key to look up in the map
• Look up value, if found write output

That translates to

val f1 = Source fromFile "file1.csv" getLines
val f2 = Source fromFile "file2.csv" getLines
val map = f2.map(_.split(", *")).map(arr => arr.init.mkString(", ") -> arr.last}.toMap
for {
  line <- f1
  key = line.split(", *").init.mkString(", ")
  value <- map.get(key)
} {
  out.write(line + ", " + value + "\n")
}