Procs and lambdas

I know this question is quite old now, but in case others run across it...

From the example in the video it looks like invoking a proc (via .call) is what I would term in-line code in other languages. That is, the proc is a short-cut way to add some lines of code at the same level/context. That is why the 'return' inside the proc ends the method. It is just like those lines of code from the proc were typed into the method, so when a return is encountered the method returns.

The lambda is more like a method call inside another method, so it dives into its own context and processes its code then returns to the outer method code. Thus, when a return is encountered in the lambda code it just exits the lambda, not the outer method.

A lambda and a block are two very different constructs. A lambda is a representation of a method whereas a block (more formally, a Proc (which is short for process)) is a representation of a snippet of code, a process.

Since a lambda is a method in its own right, it has its own return value and its own scope. A Proc does not have its own return value and if it contains a return statement the Proc will cause the enclosing method to return.

For more information: http://www.robertsosinski.com/2008/12/21/understanding-ruby-blocks-procs-and-lambdas/

@Lorinda,

I see your confusion also. The video transcript says "while if you use a lambda it will return only from the lambda." I may not have the proper terminology, but the examples seems to show that when using a proc inside a method, returns will be executed by the proc. When using a lambda though, return statements will only be executed by the method (not the lambda). Can anyone watch this video (Programming Ruby Foundations > Procs & Lambdas > Working With Procs & Lambdas) and clarify this for us? As far as the example, I'd also assume the double return statements are only for used as an example.

@Aaron,

Thanks for your link also. At first glance I understand your comments and what the link is showing. I'm having a hard time equating that to the example in the video though. I'll keep trying to work through it, but hopefully someone at Treehouse can take a look.

Update. I think I may understand what the video is trying to say. If you use the return keyword in a proc, the proc's return statement will run, and will also stop the containing method execution. If you use the return keyword in a lambda, the lambda will return, and the containing method will continue execution. Is this correct? Any further clarification would still be awesome.

I actually found this Forum post very helpful (especially the code example): https://teamtreehouse.com/forum/returning-from-a-proc-vs-lambda