Iterating over the lines of a file

Question

I'd like to write a simple function that iterates over the lines of a text file. I believe in `2.8` one could do: ``` def lines(filename: String) : Iterator[String] = { scala.io.Source.fromFile(filename).getLines } ``` and that was that, but in `2.9` the above doesn't work and instead I must do: ``` def lines(filename: String) : Iterator[String] = { scala.io.Source.fromFile(new File(filename)).getLines() } ``` Now, the trouble is, I want to compose the above iterators in a `for` comprehension: ``` for ( l1 <- lines("file1.txt"); l2 <- lines("file2.txt") ){ do_stuff(l1, l2) } ``` This again, used to work fine with `2.8` but causes a "too many open files" exception to get thrown in `2.9`. This is understandable -- the second `lines` in the comprehension ends up opening (and not closing) a file for each line in the first. In my case, I know that the `"file1.txt"` is big and I don't want to suck it into memory, but the second file is small, so I can write a different `linesEager` like so:…

Accepted Answer

scala-arm provides a great mechanism for automagically closing resources when you're done with them.

```
import resource._
import scala.io.Source

for (file1 <- managed(Source.fromFile("file1.txt"));
     l1 <- file1.getLines();
     file2 <- managed(Source.fromFile("file2.txt"));
     l2 <- file2.getLines()) {
  do_stuff(l1, l2)
}
```

But unless you're counting on the contents of `file2.txt` to change while you're looping through `file1.txt`, it would be best to read that into a `List` before you loop. There's no need to convert it into an `Iterator`.

Iterating over the lines of a file

Solution

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