# Newbie questions

**URL:** <https://www.ruby-forum.com/t/newbie-questions/137829>\
**Category:** Ruby\
**Created:** [May 16, 2008, 5:52pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829 "2008-05-16T17:52:31Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 5:52pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/1 "2008-05-16T17:52:31Z")

</div>

I feel like we need a Forum called, “Ruby N.” for people like me. Is  
there one?

I am hoping someone could help me with the following (probably) simple  
questions (my nested questions are surrounded by \*\*):

1. Someone said to use the following code for getting a string and  
printing to the screen:

puts “Where do you live?”  
STDOUT.flush  
city = gets.chomp  
puts "I live in " + city

**why not just do this:**

puts “Where do you live?”  
city = gets()  
puts "I live in " + city

??

regarding STDOUT: the comment was made - STDOUT is a global constant  
which is the actual standard output stream for the program.

**but is it necessary?**

A comment was made: flush flushes any buffered data within io to the  
underlying operating system (note that this is Ruby internal buffering  
only; the OS may buffer the data as well). The usage is not mandatory  
but recommended.

**I still don’t understand why flush is recommended. Is my omission  
going to create a problem?**

**I understand chomp to remove record separators from the end, is there  
another reason besides?**

1. Is there a place I can go to learn more about regular expressions?
2. In IRB, Float::DIG =\> 15  
\*\*question: This is because float displays to 15 decimals, right?  
\*\*question: I see “::” all the time, but don’t understand it. What does  
:: mean? Is it showing hierarchy?
3. In the code below:

class NameIt  
def initialize(name)  
@name = name  
end  
def to\_s  
puts “My name is: #{@name}”  
end  
end

n1 = NameIt.new(“tom”)  
n2 = NameIt.new(“sally”)

n1.to\_s  
n2.to\_s

\*\*the last 4 lines seem very repetative. this is something I’ve wondered  
for a long time. Is there a way to compact the last 4 lines if you are  
trying to list a whole bunch of names at once using the method to\_s?

thank very much!

Jason

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<div class="post-metadata">

**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 6:38pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/2 "2008-05-16T18:38:25Z")

</div>

On Fri, May 16, 2008 at 10:52 AM, Jason L.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> STDOUT.flush  
> city = gets.chomp  
> puts "I live in " + city
> 
> **why not just do this:**
> 
> puts “Where do you live?”  
> city = gets()  
> puts "I live in " + city

or…

puts “Where do you live?”  
puts "You live in " \<\< gets

> only; the OS may buffer the data as well). The usage is not mandatory  
> but recommended.
> 
> **I still don’t understand why flush is recommended. Is my omission  
> going to create a problem?**
> 
> **I understand chomp to remove record separators from the end, is there  
> another reason besides?**
> 
> 1. Is there a place I can go to learn more about regular expressions?

I’ve occasionally found www.regexp.info useful.

> 1. In IRB, Float::DIG =\> 15  
> \*\*question: This is because float displays to 15 decimals, right?  
> \*\*question: I see “::” all the time, but don’t understand it. What does  
> :: mean? Is it showing hierarchy?

It’s the scope operator. Page 330 of the Pickaxe, 2nd Ed.

> 1. In the code below:
> 
> class NameIt  
> def initialize(name)  
> @name = name  
> end  
> def to\_s  
> puts “My name is: #{@name}”  
> end

def to\_s  
"My name is: " \<\< name  
# no puts  
end

> end
> 
> n1 = NameIt.new(“tom”)  
> n2 = NameIt.new(“sally”)
> 
> n1.to\_s  
> n2.to\_s

puts n1  
puts n2

> \*\*the last 4 lines seem very repetative. this is something I’ve wondered  
> for a long time. Is there a way to compact the last 4 lines if you are  
> trying to list a whole bunch of names at once using the method to\_s?
> 
> thank very much!
> 
> Jason

Todd

---

<div class="post-metadata">

**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 7:06pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/3 "2008-05-16T19:06:04Z")

</div>

On 5/16/08, Jason L. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> I feel like we need a Forum called, “Ruby N.” for people like me. Is  
> there one?

This one usually works fine.

> puts “Where do you live?”  
> city = gets()  
> puts "I live in " + city
> 
> ??
> 
> regarding STDOUT: the comment was made - STDOUT is a global constant  
> which is the actual standard output stream for the program.
> 
> **but is it necessary?**

probably not for a simple test application like that one.

> A comment was made: flush flushes any buffered data within io to the  
> underlying operating system (note that this is Ruby internal buffering  
> only; the OS may buffer the data as well). The usage is not mandatory  
> but recommended.
> 
> **I still don’t understand why flush is recommended. Is my omission  
> going to create a problem?**

It’s possible that on some systems, the string “Where…?” would stay  
in an internal buffer and not get printed. If that happened, your  
program would be waiting for input, but the user would have no idea  
what it wanted.  
If you wanted a robust multi-platform application, a flush would  
ensure that the string was printed.  
However, on Windows at least, your second version works just fine.

> **I understand chomp to remove record separators from the end, is there  
> another reason besides?**

Only that one. But it’s something you usually want to do.  
Imagine your last line was  
puts “I live in “+city+”, in a nice house.”  
If you didn’t chomp, you’d get a newline right in the middle of your  
sentence.  
Also something like `if (city == 'New York')` would always fail  
without the chomp.

> 1. Is there a place I can go to learn more about regular expressions?

I keep going back to “Programming Ruby”, but there are probably better  
choices.

> 1. In IRB, Float::DIG =\> 15  
> \*\*question: This is because float displays to 15 decimals, right?

Float can hold up to 15 significant digits.  
irb(main):053:0\> f= 1+ 1e-14  
=\> 1.00000000000001

irb(main):054:0\> f= 1+ 1e-15  
=\> 1.0 #can’t hold 16 digits.

irb(main):055:0\> f=1+1e14  
=\> 1.00000000000001e+014

irb(main):056:0\> f=1+1e15  
=\> 1.0e+015

> \*\*question: I see “::” all the time, but don’t understand it. What does  
> :: mean? Is it showing hierarchy?

It’s called the ‘scope operator’, it lets you Constants (including  
other classes) declared inside the definition of the Class on the left  
hand side.  
If I have:  
Class X  
Z=0  
Class Y;  
# …  
end  
end

The only way to access Y or Z is with the X:: syntax.

> n1 = NameIt.new(“tom”)  
> n2 = NameIt.new(“sally”)
> 
> n1.to\_s  
> n2.to\_s
> 
> \*\*the last 4 lines seem very repetative. this is something I’ve wondered  
> for a long time. Is there a way to compact the last 4 lines if you are  
> trying to list a whole bunch of names at once using the method to\_s?

Arrays and their iterator methods can be useful:

names = %w{ tom sally douglas} #shorthand for [“tom”,“sally”…]  
nameits = names.map {|name| NameIt.new(name) }  
nameits.each{|nit| puts n.to\_s }

names.map calls the block for each entry in names, and returns  
a new array of the same size, containg the results of the block.  
nameits.each simply calls the block once for each entry.

hope this helps,  
-Adam

---

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**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 8:38pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/4 "2008-05-16T20:38:00Z")

</div>

I found some issues with the above proposed solutions that I wanted to  
ask about:

> > class NameIt  
> > def initialize(name)  
> > @name = name  
> > end  
> > def to\_s  
> > puts “My name is: #{@name}”  
> > end
> 
> def to\_s  
> "My name is: " \<\< name  
> # no puts  
> end
> 
> > end

Clarifications/comments:

it appears that \<\< name needs to be changed to \<\< @name for it to work.  
I assume this is because the scope of “name” is only known in the  
initialize method and not the to\_s method? I understand the scope of the  
instance variable to be visible throughout the class. Is this the  
reason?

Another question:

I entered this in:  
class NameIt  
def initialize(name)  
@name = name  
end  
def to\_s  
puts "My name is: " \<\< @name  
end  
end  
names = %w( tom sally doug john)  
nameits = names.map {|name| NameIt.new(name)}  
nameits.each{|n| puts n.to\_s}

and it returned this:

> 

My name is: tom  
nil  
My name is: sally  
nil  
My name is: doug  
nil  
My name is: john  
nil

> Exit code: 0

Where did the nil come from?

Thanks! Jason

---

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**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 7:29pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/5 "2008-05-16T19:29:27Z")

</div>

Thank you! Yes, very helpful.

the \<\< operator is great:

And the map method is also great!

---

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**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 10:14pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/6 "2008-05-16T22:14:54Z")

</div>

On Fri, May 16, 2008 at 1:38 PM, Jason L.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > 
> 
> I assume this is because the scope of “name” is only known in the  
> initialize method and not the to\_s method? I understand the scope of the  
> instance variable to be visible throughout the class. Is this the  
> reason?

Yep. You are correct. Sorry 'bout that.

> Another question:
> 
> I entered this in:  
> class NameIt  
> def initialize(name)  
> @name = name  
> end  
> def to\_s  
> puts "My name is: " \<\< @name  
> end

Leave out the puts in #to\_s. You want #to\_s to return a string, not  
execute a console output.

> end  
> names = %w( tom sally doug john)  
> nameits = names.map {|name| NameIt.new(name)}  
> nameits.each{|n| puts n.to\_s}

#puts calls #to\_s, so you doing…

puts n.to\_s

…is redundant. Just do…

puts n

hth,  
Todd

---

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**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 17, 2008, 12:12am UTC](https://www.ruby-forum.com/t/newbie-questions/137829/7 "2008-05-17T00:12:51Z")

</div>

Perfect. Thank you both!

---

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**Author:** ![leveille](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/a88e57/32.png) [@leveille](https://www.ruby-forum.com/u/leveille)\
**Post date:** [May 16, 2008, 10:28pm UTC](https://www.ruby-forum.com/t/newbie-questions/137829/8 "2008-05-16T22:28:28Z")

</div>

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On May 16, 2008, at 8:38 PM, Jason L. wrote:

> nameits.each{|n| puts n.to\_s}  
> nil
> 
> > Exit code: 0
> 
> Where did the nil come from?

To give you a more elaborate answer on why “nil” is printed… Lets  
isolate that case:

===  
def foo  
puts “bar”  
end

# puts foo

This prints

bar  
nil

Why? The Method #puts prints to standard out _and returns nil_. (in  
Ruby 1.8.6, that will change in 1.9).

Every statement and method in Ruby has a return value. In the case of  
Methods, the return value is eighter explicitly  
stated or the value of the last statement in the method body. So the  
#foo returns nil. As you call #puts again  
on the return value of foo, you get the string representation of nil.  
Which is… “nil”.

So you essentially wrote:

puts(puts(“bar”))

Regards,  
Florian G.

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