I have seen this link about associated array in Ruby, and I know, it is completely like php.
But take a look at this piece of code:
x=[1,"Jef",:three]
it is clear that x[1]="jef", but the question is:
What is the role of :three.
I gussed it should be a key with a nill value, and i changed the code to this
x=[1,"Jef",:three,4]
and when i run it, I faced with this error:
no implicit conversion of Symbol into Integer (TypeError)
so what are the roles of : and three here?
I think you're confusing arrays with hashes. In this particular example
x = [1,"Jef",:three,4]
incidently x[1] is equal to "Jef", but thats because element at 1st index of x is "jeff" (which should be obvious as x is an Array), not because every two elements are key value pairs as in a a Hash.
The error
no implicit conversion of Symbol into Integer (TypeError)
is probably because you tried something like x[:three], which is obviously invalid.
This could work if your x looks something like this.
x = { 1 => "Jef", :three => 4 }
Then x[:three] will result in desired result 4.
Remember Arrays and Hashes in Ruby are two different concepts.
:three is a Symbol which are essentially strings with few twists.
Suggestion : If you want to learn basic Ruby stuff you can read up on Rubymonk. I has great content.
:three is a symbol and it's just a regular member of a regular array. Associative arrays in Ruby are something different and they're called hashes.
