Link to explanations of r-value, l-value and lint

[vks]

I think those terms are not common knowledge for a lot of readers, so I linked the corresponding Wikipedia articles. We might even want to consider explaining them in Rust by Example.

[japaric]

@mdinger

Do these wikipedia links look "good enough" to you? Or are they too general/abstract?

Also, could you edit the first comment of issue #97 so that it renders as a TODO list (like issue #1)

---

We might even want to consider explaining them in Rust by Example.

We could add a (single page) glossary to the book, in the same spirit of the rusticon, for terms that may be unfamiliar; and then link these terms to it (using anchors). Opinions on this?

[vks]

I think the links are better than nothing (they give background on where those words come from). This pull request addresses the in my opinion worst offenders from issue #97.

A better solution would be a glossary that includes one-sentence definitions and the links.

[mdinger]

I think both links are definitely better than nothing. Neither is really bad. The text for r-value/l-value is heavy and abstract but you can understand it if you think about it. It doesn't have lots of unknown words which raise the difficulty. I would add them at least until there is a glossary or something to help out.

I tried to form their example text into code. Hopefully it emphasizes that it's mainly talking about right/left sides on an equation. You have to read pretty carefully to realize this:

// This gives 13i as an `r-value` (right side) and then is discarded (not stored)
9i + 4i;
// `x` is an `l-value` (left side). The previous `r-value` is assigned to it (stored)
let x = 9i + 4i;
// A function can only call an `l-value` because it has a storage location
// An `r-value` has no storage location and therefore cannot be called
f(x)
f(`r-value?`) // Doesn't work...how could you call it?

A glossary section with term definitions would probably be a good idea in the long run.

[mdinger]

Also, could you edit the first comment of issue #97 so that it renders as a TODO list (like issue #1)

Done

[vks]

f(r-value?) // Doesn't work...how could you call it?

You can actually have an r-value as an argument to a function: f(9i + 4i)

(This is pretty important in C++11 and it's move semantics, because r-values can be moved instead of copied (because they cannot be reused), which is more efficient.)

[mdinger]

Interesting. Didn't think about that. Was thinking about cases like this:

13i; // Let's pass this to f next line
f(`previous line`) // can't because it was discarded

[japaric]

Ok, let's merge this for now, until we start working on the glossary (#97)