can't run .scala file from REPL? - scala

Question

I'm newly at Scala.
I want to run function which is wrote at my file while.scala:
def whileLoop {
var i = 1
while(i <= 3) {
println(i)
i += 1
}
}
whileLoop
here is how it looks at REPL:
scala> scala /home/nazar/Downloads/while.scala
<console>:1: error: illegal start of simple expression
If I understood right from book. I need to specify .scala file location and run with:
scala /path/to/file.scala
Why it fails?
Here is snippet from book:
You can run the code like this:
batate$ scala code/scala/while.scala
1
2
3
UPDATE:
I tried options :load it works, but when I want to run another file for_loop.scala:
def forLoop {
println( "for loop using Java-style iteration" )
for(i <- 0 until args.length) {
println(args(i))
}
}
forLoop
it fails:
scala> :load /home/nazar/Downloads/for_loop.scala
Loading /home/nazar/Downloads/for_loop.scala...
<console>:9: error: not found: value args
for(i <- 0 until args.length) {
^
<console>:8: error: not found: value forLoop
forLoop
^
scala> :load /home/nazar/Downloads/for_loop.scala hello scala
That file does not exist
How to solve this trouble?

Answer 1

You do it like this, from the shell / command line, not from within the REPL (% is nominal shell prompt):
% scala MyScalaScriptName.scala
You did this:
% scala
scala> scala while.scala
<console>:1: error: illegal start of simple expression
The only thing known within the Scala REPL is Scala code itself and a few built-in special commands. However, one of them will do what you want:
% cd
% scala
scala> :load Downloads/while.scala
Loading Downloads/while.scala
1
2
3

Answer 2

In order to use command line arguments (via args) it is needed to extend App or more commonly to define a principal or main method in an object, namely a def main(args: Array[String]) method, which defines an entry point to the program. Consider for instance
object AnyName extends App {
def forLoop {
println( "for loop using Java-style iteration" )
for(i <- 0 until args.length) {
println(args(i))
}
}
forLoop
}
AnyName.main(Array("first","second"))
Try to load it from REPL. The other approach is thus,
object AnyName {
def main(args: Array[String]) {
println( "for loop using Java-style iteration" )
for(i <- 0 until args.length) {
println(args(i))
}
}
}
AnyName.main(Array("first","second"))
In this latter example, note the scope of args, bound to the parameter in main.