Help me decipher this output

Question

Hi,

I have started learning Ruby recently and I was trying out the following piece of code.

a=[1,2]
b='slam dunk'
a.each { |b| c=a*b; puts c;}

I am getting the following output. I have no clue why. I expected an error or something to be thrown. Can someone explain me why this happens?

1
2
1
2
1
2

Thanks

Answer 1

The block variable b overwrites "slam dunk", so what happens is

c=[1,2]*1 # => [1,2]
c=[1,2]*2 # => [1,2,1,2]

This is what you see in the output

Answer 2

First I will try to explain the output you're seeing.

In ruby if we have an array e.g. [1, 2] and multiply it by a number n then you get the array repeated n times e.g.

irb(main):012:0> [1,2] * 2
=> [1, 2, 1, 2]

So your each loop prints [1, 2] * 1 followed by [1, 2] * 2

If you are asking why having b assigned to a string and then assigned to a number doesn't generate an error then this is not a problem in dynamically typed languages like ruby. e.g.

irb(main):017:0> a = 5
=> 5
irb(main):018:0> a = 'no problem'
=> "no problem"

After your each loop b will just have the last value it had in the loop i.e. 2

Answer 3

I think outer b has no effect inside loop.
On the first cycle you print your array once.
On the second cycle your print your array two times

Answer 4

When evaluating the each the variable b that was originally assigned the value is hidden by the b argument to the block.

So what the each loop actually receives on each pass is

 [1,2] * 1 #1st Pass
 [1,2] * 2 #2nd Pass

So the 1st pass prints 1 2 and the 2nd pass prints 1 2 1 2 (i.e. it prints the array twice)