Types in Scala, Long, Int, etc.

Question

Please type this in.

scala> 86400000 * 150 res0: Int = 75098112   scala> val i : Long = 86400000 * 150 i: Long = 75098112     val i  = 86400000 * 150.asInstanceOf[Long] i: Long = 12960000000  val i  = 86400000 * 150L i: Long = 12960000000 

What in the world is going on here? I've been skydiving and I must say that this is the most dangerous thing I've ever seen. No compiler check for this? Obviously if I was substituting 150 for a variable that's different.

*EDIT*

This was the actual code that got me worried.

val oneDay = 86400000 val days150 = oneDay * 150  days150 = 75098112 

This was not Scala's fault or anyones fault except my own. Just got me worried.

Answer 1

There's nothing Scala-specific about this. It's just a matter of the target type of the assignment being irrelevant to the type in which an operation (multiplication in this case) is performed.

For example, in C#:

using System;  class Program {     static void Main(string[] args)     {         int a = unchecked(86400000 * 150);         long b = unchecked(86400000 * 150);         long c = 86400000 * (long) 150;         long d = 86400000 * 150L;         Console.WriteLine(a); // 75098112         Console.WriteLine(b); // 75098112         Console.WriteLine(c); // 12960000000         Console.WriteLine(d); // 12960000000     } } 

The unchecked part here is because the C# compiler is smart enough to realize that the operation overflows, but only because both operands are constants. If either operand had been a variable, it would have been fine without unchecked.

Likewise in Java:

public class Program {     public static void main(String[] args)     {         int a = 86400000 * 150;         long b = 86400000 * 150;         long c = 86400000 * (long) 150;         long d = 86400000 * 150L;         System.out.println(a); // 75098112         System.out.println(b); // 75098112         System.out.println(c); // 12960000000         System.out.println(d); // 12960000000     } }