Errata for Programming Ruby 1.9

#40856: For the section Splat! Expanding Collections in Method Calls, the 1.9 marker is in front of the paragraph "When you call a method . . ."

This does work in 1.8.6,7, but the splat has to be at the end. In other words, a reader might be misled to think the the basic functionality is missing in earlier versions, while only 1.9 lets you have multiple splats in different orders.
--John

#40154: I read: "String literals are always encoded using the encoding of the source file that contains them, regardless of the content of the string".

But, actually, I'm trying it and it doesn't behave like that.

# coding: utf-8
puts __ENCODING__
puts "ciao".encoding.name
puts "ciao \u03c0".encoding.name

Executing, it produces:
UTF-8
US-ASCII
UTF-8

So, that phrase and the following example aren't correct.

If it is relevant, this is my ruby version:
roby@debian-roby:~$ ruby -v
ruby 1.9.0 (2008-06-20 revision 17482) [i486-linux]
--Roberto Casadei

#39554: The paragraph under 'Interactive Configuration' says: "For example to change your prompt back to DEFAULT you could use the following:" but then the code is 'conf.prompt_mode = :SIMPLE'.--Octav Popescu

#41973: The source code of modified excel2.rb is not working, it throws exception:
excel2.rb:7:in `[]=': (in OLE method `visible': ) (WIN32OLERuntimeError)
OLE error code:0 in <Unknown>
<No Description>
HRESULT error code:0x8002000e
Invalid number of parameters.
from excel2.rb:7:in `<main>'

I found excel['Visible'] = true should be
excel.visible = true

I also found excelchart['rotation']= rot is not working,
it should be excelchar.rotation = rot, so I think the earlier code snippet is also wrong:
...
excelchart['Rotation'] = 45

which means we can not use Ruby hash notation to set the properties.

Following are the correct code:

require 'win32ole'
# -4100 is the value for the Excel constant xl3DColumn
ChartTypeVal = -4100

excel = WIN32OLE.new("excel.application")

#excel['visible'] = TRUE
excel.visible = true
excel.Workbooks.Add()
excel.Range("a1").value = 3
excel.Range("a2").value = 2
excel.Range("a3").value = 1
excel.Range("a1:a3").Select()
excelchart = excel.Charts.Add()
excelchart.type= ChartTypeVal

30.step(180,5) do |rot|
excelchart.rotation = rot
#excelchart['Rotation'] = rot
sleep(0.1)
end

excel.ActiveWorkbook.Close(0)
excel.Quit()
--Steve Zhang

#41976: The code of win32_15.rb is not working, it throws following exception:

win32_15.rb:15:in `[]': wrong number of arguments(2 for 1) (ArgumentError)
from win32_15.rb:15:in `<main>'

--Steve Zhang

#39185: I can not reproduce the behavior of class variable as described on pages 337 and 338 of Programming Ruby 1.9.

Here is a file with Ruby code I typed in from the text:

##### begin classvars.rb
class Holder
@@var = 99
def Holder.var=(val)
@@var = val
end
def var
@@var
end
end

@@var = "top level variable"

a = Holder.new
puts "a.var: #{a.var}"
Holder.var = 123
puts "a.var: #{a.var}"

def a.get_var
@@var
end

puts "a.get_var: #{a.get_var}"
puts "@@var: #{@@var}"
##### end classvars.rb

(Essentially, this is the code from the text using puts to produce output. Also, at the end, I show the value of the top level variable @@var.)

Here is the Ruby version and the output I see:

$ ruby -v
ruby 1.9.1p0 (2009-01-30 revision 21907) [i686-linux]
$ ruby classvars.rb
a.var: top level variable
a.var: 123
a.get_var: 123
@@var: 123--Kenneth Ballou (ballou@crab.mv.com)

#39186: With respect to erratum #39185, I tried the same code on an older Ruby build:

$ ruby -v
1.9.0 (2006-06-08) [x86_64-linux]

With this version, the output agrees with the text:

$ ruby1.9 classvars.rb
a.var: 99
a.var: 123
a.get_var: top level variable
@@var: top level variable

Perhaps this is a Ruby bug in 1.9.1p0 instead of a book erratum?--Kenneth Ballou

#39435: The second paragraph for section "break, redo, next, and retry" says: "retry restarts the loop, reevaluating the condition." However on page 147 there's a footnote saying "Prior versions of Ruby also supported the retry keyword as a looping mechanism. This has been removed in Ruby 1.9."--Octav Popescu

#39292: Description of $stdout states: "Assignment to $stdout is not permitted: use $stdout.reopen instead."

I believe this is not exact. STDOUT can't be reassigned (obviously since it is a constant), but $stdout is a variable and has STDOUT as default value, but can be reassigned. See The Ruby Programming Language, for intance to section 9.7.1.4, or search ruby's source code for "$stdout = "--Marc-Andre Lafortune

#40570: The retry keyword is still mentioned in the section 'break, redo, next, and retry' as a control flow modifier for loops, but retry is not valid for loop control in 1.9 (although this fact is mentioned earlier in the exception handling topic as a footnote) --Janos Sebok

#40833: The section headed "break, redo, next, and retry" says:

"If used within a while, until, or for loop, the value given to break is returned as the value of the statement, and the value given to next is silently ignored. "

This is not correct in the case of a for loop, as demonstrated by this code:

class Foo
def each
p yield
p yield
p yield
end
end

f = Foo.new
for i in f
next "next"
end

Running it produces this output:

"next"
"next"
"next"

which shows that the value given to "next" is not "silently ignored', but rather is returned as the value of "yield".

--Ron Newman

#39445: Second paragraph for 'Calling a Proc' says: "You can also invoke a proc using the syntax name.(args...). This is mapped internally into a.call(...)." Who's 'a' and where do 'name' and 'args' go? Maybe it wants to say "name.call(args...)"?--Octav Popescu

#40810: names = %{ant bee cat}

results in the string "ant bee cat". What you want instead is

names = %w{ant bee cat}

which results in ["ant", "bee", "cat"}

Without this fix, the following statement

result = names.map {|name| name.upcase}

makes no sense, since ".map" is something you do to an array (or other Enumerable), not to a String.

--Ron Newman

#40841: In section "instance_eval and class_eval",

First paragraph says: "The methods Object#instance_eval, Object#class_eval, and Object#module_eval"

Those last two should actually be Module#class_eval and Module#module_eval--Ron Newman

#41001: "Previously it was impossible to pass a local or instance variable into a block..." shouldn't say "local" since those are captured by the closure when using blocks. Since the _exec methods don't allow for strings, this is always the case.--Tim Caswell

#41075: Running the code in ruby 1.9.1 with -W2 gives a warning of "method redefined". (See gist 217992) I'm not sure which of undef_method or remove_method should be used to avoid the warning, though.--Andrew Grimm

#39188: Hash.[] has two other forms. The second and third form take a single argument which is either an array of key-value pairs or an object convertible to a hash.

See redmine #1385, confirmed ruby-core #23433--Marc-Andre Lafortune

#39050: Oups, sorry, I meant to say Numeric#step returns an enumerator if no block is given (in Ruby 1.9), so the interface should change, and a "1.9" symbol should be added.--Marc-Andre Lafortune

#39135: The 'members' instance method of Struct returns an array of symbols rather than strings, and this is a change in 1.9.

members joe.members →array
Returns an array of strings (s/b symbols) representing the names of the instance variables.
Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.members # => [:name, :address, :zip]--Garold L Johnson

#41295: 'rb_global_variable' takes a pointer as its argument.

This section...
static VALUE obj;
// ...
obj = rb_ary_new();
rb_global_variable(obj);

...should be replaced with something along the lines of:
static VALUE obj;
rb_global_variable(&obj);
// ...
obj = rb_ary_new();
--Cornelius Reiber