scala quirky in this while loop code -

yesterday, piece of code caused me headache. fixed reading file line line. ideas ?

the while loop never seems executed though no of lines in file greater 1.

 val lines = source.fromfile( new file("file.txt") ).getlines;   println( "total lines:"+lines.size );   var starti = 1;  while( starti < lines.size ){    val nexti = math.min( starti + 10, lines.size  );     println( "batch ("+starti+", "+nexti+") total:" + lines.size )    val linessub = lines.slice(starti, nexti)    //do linessub    starti = nexti  } 

this indeed tricky, , it's bug in iterator. getlines returns iterator proceeds lazily. seems happen if ask lines.size iterator goes through whole file count lines. afterwards, it's "exhausted":

scala> val lines = io.source.fromfile(new java.io.file("....txt")).getlines lines: iterator[string] = non-empty iterator  scala> lines.size res4: int = 15  scala> lines.size res5: int = 0  scala> lines.hasnext res6: boolean = false 

you see, when execute size twice, result zero.

there 2 solutions, either force iterator 'stable', lines.toseq. or forget size , "normal" iteration:

while(lines.hasnext) {   val linessub = lines.take(10)   println("batch:" + linessub.size)   // linessub }