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Compilation errors

1 reply on 1 page. Most recent reply: Sep 3, 2008 10:24 PM by Bill Venners

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Leif Jantzen

Posts: 2
Nickname: ljantzen
Registered: Aug, 2005

Compilation errors

Posted: Aug 27, 2008 1:23 PM

Hi,

I am reading through the new (version 4) edition of the PrePrint book. I am having some trouble with a few of the code examples:

On page 161 the try expression example fails compilation ( 2.7.2.RC1 ) when I paste the code into the interpreter:


scala> val n = 3
n: Int = 3

scala> val half =
     | if (n % 2 == 0)
     | n / 2
half: Unit = ()

scala> else
<console>:1: error: illegal start of definition
       else
       ^

scala> throw new RuntimeException("n must be even")

Additionally, the tail recursion example on page 191 fails to compile:


scala> def boom(x: Int): Int =
     | if (x == 0) throw new Exception("boom!")
<console>:5: error: type mismatch;
 found   : Unit
 required: Int
       if (x == 0) throw new Exception("boom!")
       ^

scala> else boom(x - 1) + 1
<console>:1: error: illegal start of definition
       else boom(x - 1) + 1
       ^

Am I missing something here?

Bill Venners

Posts: 2284
Nickname: bv
Registered: Jan, 2002

Re: Compilation errors

Posted: Sep 3, 2008 10:24 PM

Hi Leif,

I think this is caused by the interpreter guessing wrongly where the end of your phrase is. If you put these things as is in a file and compile them, they will work. Or if you reformat them so the else is on the same line as the previous line, it should work in the interpreter too.

Bill

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