Scala doesn't have lazy evaluation of function arguments, it's got call-by-name. The difference is that lazy evaluation caches the value an argument evaluates t

Scala doesn't have lazy evaluation of function arguments, it's got call-by-name. The difference is that lazy evaluation caches the value an argument evaluates to the first time it is needed, so it's evaluated at most once, whereas call-by-name simply passes the parameter unevaluated and the result of evaluation is not cached, so might be computed more than once. Consider this Scala program object Main extends { def tryit [ T ] ( block : => T ) : Unit = { println ( "----- Running 1st block -----" ) block println ( "----- Running 2nd block -----" ) block println ( "--------- Finished ----------" ) } def main ( args : Array [ String ] ) { var i = -1 tryit ( { i += 1; println ( s"i = $i" ) } ) } }