Basic question about blocks

7stud2 · 13 May 2013 14:03

Hello forum,

I am new to Ruby and have a question about blocks.

A) Below is the code I have put in a file <blocksexample.rb>:

···

---------------------------------------------------
# Script block2.rb
def simpleFunction
yield
yield
end

animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
---------------------------------------------------

B) I run the <blocksexample.rb> as below....only once:
---------------------------------------------------
C:\RUBYEX~1>blocksexample.rb
---------------------------------------------------

C) The output is as below:
---------------------------------------------------
Hello, Tiger
Hello, Giraffe
It's 5 characters long!
It's 7 characters long!
---------------------------------------------------

Question 1: How is it I am not getting error for using same name
<animals> for 2 blocks in the same <rb> file?
Question 2: How is the first animal block executed followed by the
second animal block execution...inspite of me running the example only
once...

Please let me know, appreciate your help in advance.

Esh

--
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Josh_Cheek · 13 May 2013 14:19

Can you check the program you posted? There is no animals method, so it
blows up on my computer.

-Josh

···

On Mon, May 13, 2013 at 9:03 AM, Esh Gun <lists@ruby-forum.com> wrote:

Hello forum,

I am new to Ruby and have a question about blocks.

A) Below is the code I have put in a file <blocksexample.rb>:

---------------------------------------------------
# Script block2.rb
def simpleFunction
yield
yield
end

animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
---------------------------------------------------

B) I run the <blocksexample.rb> as below....only once:
---------------------------------------------------
C:\RUBYEX~1>blocksexample.rb
---------------------------------------------------

C) The output is as below:
---------------------------------------------------
Hello, Tiger
Hello, Giraffe
It's 5 characters long!
It's 7 characters long!
---------------------------------------------------

Question 1: How is it I am not getting error for using same name
<animals> for 2 blocks in the same <rb> file?
Question 2: How is the first animal block executed followed by the
second animal block execution...inspite of me running the example only
once...

Please let me know, appreciate your help in advance.

7stud2 · 13 May 2013 14:33

The order of execution is correct, you're calling "animals" twice, and
in each case you're getting "Tiger" and "Giraffe" before moving on the
next call of "animals".

···

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7stud2 · 13 May 2013 14:51

Or this:

animals { |x| puts "Hello, #{x}\nIt's #{x.length} characters long!" }

···

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7stud2 · 13 May 2013 15:47

Yes, thats what I thought

Thanks Ulises and everybody.

So long,
Esh

···

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7stud2 · 13 May 2013 14:28

Josh,

Sorry for mistake in typing the code...below is the program code...

···

--------------------------------------------
# Script block1.rb
def animals
yield "Tiger"
yield "Giraffe"
end

animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
--------------------------------------------

And the Yield function in above ...
- first yields to the .... animals { |x| puts "Hello, #{x}" } for
"Tiger"
- then the same "Tiger" should go to the ... animals { |x| puts "It's
#{x.length} characters long!" }

.... this is my understanding...but the code prints out as below:

Hello, Tiger
Hello, Giraffe
It's 5 characters long!
It's 7 characters long!

...Meaning the
- first animals block executes for the word "Tiger" and "Giraffe"
FOLLOWED BY
- second animals block executes for the word "Tiger" and "Giraffe"

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7stud2 · 13 May 2013 14:37

Joel Pearson wrote in post #1108788:

The order of execution is correct, you're calling "animals" twice, and
in each case you're getting "Tiger" and "Giraffe" before moving on the
next call of "animals".

Sorry but I am trying to understand the flow here...

1) First yield "Tiger" should call
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }

2) Second yield "Giraffe" should call
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }

But the output is NOT...
Hello, Tiger
It's 5 characters long!
Hello, Giraffe
It's 7 characters long!

The output IS...

Hello, Tiger
Hello, Giraffe
It's 5 characters long!
It's 7 characters long!

···

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7stud2 · 13 May 2013 15:00

Joel Pearson wrote in post #1108793:

Or this:

animals { |x| puts "Hello, #{x}\nIt's #{x.length} characters long!" }

Ok. Let me undersdtand this...

1) I was thinking the <Tield> in the below <animals> function

···

--------------------------------------------
def animals
yield "Tiger"
yield "Giraffe"
end
--------------------------------------------

... calls each of the <animals> blocks below with "Tiger" and "Giraffe"

--------------------------------------------
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
--------------------------------------------

2) But I think from all the explanations I got... below might be true

--------------------------------------------
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
--------------------------------------------

... calls the <animals> function

--------------------------------------------
def animals
yield "Tiger"
yield "Giraffe"
end
--------------------------------------------

Does this make any sense ?

Esh

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Wayne_Brisette · 13 May 2013 14:43

Actually, Ruby is doing exactly what you are asking it to do.

You need to rewrite your block to get what you are looking for.

animals { |x| puts "Hello, #{x}\nIt's #{x.length} characters long!" }

When you were calling animals, it stepped through both yields. That's expected. Why do you think it should have been otherwise?

Wayne

ulises · 13 May 2013 14:47

The output is correct, to get what you want to change the sentence:

animals { |x| puts "Hello, #{x}"; puts "It's #{x.length}
characters long!" }

Saludos,
Ulises

···

2013/5/13 Esh Gun <lists@ruby-forum.com>:

Joel Pearson wrote in post #1108788:

The order of execution is correct, you're calling "animals" twice, and
in each case you're getting "Tiger" and "Giraffe" before moving on the
next call of "animals".

Sorry but I am trying to understand the flow here...

1) First yield "Tiger" should call
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }

2) Second yield "Giraffe" should call
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }

But the output is NOT...
Hello, Tiger
It's 5 characters long!
Hello, Giraffe
It's 7 characters long!

The output IS...

Hello, Tiger
Hello, Giraffe
It's 5 characters long!
It's 7 characters long!

--
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ulises · 13 May 2013 15:38

You call twice the animal function. The first time sent "puts "Hello,
#{x}"" as a block and the second time "puts "It's #{x.length}
characters long!"".

Saludos,
Ulises

···

2013/5/13 Esh Gun <lists@ruby-forum.com>:

Joel Pearson wrote in post #1108793:

Or this:

animals { |x| puts "Hello, #{x}\nIt's #{x.length} characters long!" }

Ok. Let me undersdtand this...

1) I was thinking the <Tield> in the below <animals> function

--------------------------------------------
def animals
       yield "Tiger"
       yield "Giraffe"
end
--------------------------------------------

... calls each of the <animals> blocks below with "Tiger" and "Giraffe"

--------------------------------------------
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
--------------------------------------------

2) But I think from all the explanations I got... below might be true

--------------------------------------------
animals { |x| puts "Hello, #{x}" }
animals { |x| puts "It's #{x.length} characters long!" }
--------------------------------------------

... calls the <animals> function

--------------------------------------------
def animals
       yield "Tiger"
       yield "Giraffe"
end
--------------------------------------------

Does this make any sense ?

Esh

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