Avoiding Overflow

Question

This Stackoverflow post discusses the potential problem of a numeric overflow if not appending L to a number:

Here's an example from the REPL:

scala> 100000 * 100000 // no type specified, so numbers are `int`'s
res0: Int = 1410065408

One way to avoid this problem is to use L.

scala> 100000L * 100000L
res1: Long = 10000000000

Or to specify the number's types:

scala> val x: Long = 100000
x: Long = 100000

scala> x * x
res2: Long = 10000000000

What's considered the best practice to properly specify a number's type?

This is really an opinion question. There is no universally accepted best practice for this. I'd just use the L suffix. — Jesper
– Jesper, Commented Jan 27, 2014 at 16:10
This isn't a matter of opinion. Adding an L specifies the right type, using ascription converts it afterwards. — Daniel C. Sobral
– Daniel C. Sobral, Commented Jan 27, 2014 at 18:27

Daniel C. Sobral · Accepted Answer · 2014-01-27 17:34:17Z

10

You should always use L if you are using a long. Otherwise, you can still have problems:

scala> val x: Long = 10000000000
<console>:1: error: integer number too large
       val x: Long = 10000000000
                     ^

scala> val x = 10000000000L
x: Long = 10000000000

The conversion due to type ascription happens after the literal has been interpreted as Int.

answered Jan 27, 2014 at 17:34

Daniel C. Sobral

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2 Comments

Kevin Meredith Over a year ago

Why doesn't 100000 * 100000 get stored in a data structure that can hold the value without overflowing? Is it a high burden on the programming language writer?

Daniel C. Sobral Over a year ago

@KevinMeredith In some languages, it does. Scala follows Java convention and types, which was inherited from C by way of C++, and defaults to numeric types that can be efficiently manipulated by the CPU -- with direct translations into machine code, often enough.

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