Ah, ok; that didn't seem related to this specific discussion of yield (yield is valuable to have as an expression even in a multi-statement function), but I can see how it is reminiscent.

It should be noted, though, that when you use the lambda keyword, the result is a function, and has the same properties and behaviors as a function (including that it can contain yield and be a generator).

The lambda syntax is simply a way to declare a function as an expression. You can't have a multi-statement block embedded in an expression due to fundamental limitations of normative whitespace.

There really, though, is only one kind of "callable": "function". There are two syntaxes for declaring it, however: "def", which takes a block of statements, and "lambda", which takes an expression.

This is (to me) drastically different than the behavior difference that I believe is what you are referring to in Ruby, where Proc and lambda have different semantics for embedded usages of the "return" keyword.

(That said, I want to be clear, to both you and any random audience: I personally agree with Ruby's decision to have these two forms of callable, per real-world conversations I've had with wycats.)

(afterword) Someone else might find this interesting: I was going to also make the point that both lambda and def result in the same class (function), but it turns out that Proc.new and lambda do as well (Proc).