For sure?

I think that while I was in Canada, I came across this particular phrase very often: "For sure!"

I'd hear it as I ordered my meal:
Me: "Can I have the enchilada please?"
A: "For sure!"

And I just heard it when I was talking to my friend:
Me: "Let's meet up for lunch sometime!"
K: "For sure!"

The question here is, what is the meaning of the word "sure" in this case? Is it an expletive? Or is it taking the position of a adjective? I decided to check up the meaning of "sure"...

Turns out that "sure" is actually polysemic; it can function as both an adjective and an adverb.

Under the meanings of "sure" as an adjective, I came across this:

for sure

a) informal certainly or definitely:

No one knows for sure what really happened.

b) spoken used to emphasize that something is true:

We'll always need teachers, that's for sure.

c) American English informal spoken used to agree with someone

And I realise that in these cases, "for sure" is actually used as an embedded prepositional phrase. But when we use it separately, where "for sure" stands alone, it still has the same meaning of certainly or definitely.

I decided to think of other such phrases, and realise that "for sure" falls into the same category as phrases such as "of course" and "for certain" and "you bet!". I wonder if there's a category for such phrases... maybe we could call them "exclaimatives".

And then I wonder what's the Singlish equivalent... and I believe that it would be "like duh!" or "can lah!".

Interesting how these things come about..