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Naive Question

4 replies on 1 page. Most recent reply: Nov 23, 2008 7:04 PM by Vladimir Kelman

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Ian Coleman

Posts: 3
Nickname: 56491
Registered: Jun, 2008

Naive Question

Posted: Jun 24, 2008 9:39 AM

I ran the first example through the Scala intepreter (please don't laugh):


#!/usr/bin/env scala
!#

var capital = Map("US" -> "Washington", "Japan" -> "Tokyo")
capital += ("France", "Paris")
println(capital("France"))

The text says, "The notation in this example is
high-level, to the point, and not cluttered with extraneous semicolons or type annotations." And I agree. But it also fails to run. :)

I'm assuming this is *not* valid Scala code?

Ian Coleman

Posts: 3
Nickname: 56491
Registered: Jun, 2008

Re: Naive Question

Posted: Jun 24, 2008 9:40 AM

Sorry, error message would be helpful:


(fragment of fpa.scala):3: error: value += is not a member of scala.collection.immutable.Map[java.lang.String,java.lang.
String]
capital += ("France", "Paris")
         ^
one error found
!!!
discarding <script preamble>

Bill Venners

Posts: 2284
Nickname: bv
Registered: Jan, 2002

Re: Naive Question

Posted: Jun 24, 2008 2:13 PM

Hi Ian,

I think you mistyped the second line from the book. It should be:

capital += ("Japan" -> "Tokyo")

You have a comma where the -> should be.

Ian Coleman

Posts: 3
Nickname: 56491
Registered: Jun, 2008

Re: Naive Question

Posted: Jun 24, 2008 2:28 PM

You have a comma where the -> should be.

Thanks, Bill. I knew it was something stupid.

It's funny, I'm really at square one here. I feel like I'm just transcribing hieroglyphs... ;)

--ian

Vladimir Kelman

Posts: 46
Nickname: vkelman
Registered: Feb, 2008

Re: Naive Question

Posted: Nov 23, 2008 7:04 PM

By the way, Ian, you could write
capital += (("France", "Paris"))
and it would work as well, although this syntax is less obvious. A "Map.+=()" requires a tuple as parameter. This tuple could be created as "France" => "Paris" or as ("France", "Paris"). These two forms are equivalent, if I'm not mistaken.

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