Add an example of converting a string to an int

[nham]

The Rust cheatsheet was recently removed (see here) in favor of Rust by Example. One thing I used the cheatsheet for repeatedly, because I can never remember it for some reason, is how to convert a string to an int. Rust by Example does not appear to have such an example, or at least I was not able to find it by searching both on the site and on Github.

[japaric]

Rust by Example does not appear to have such an example

We don't have it at the moment. (Would you volunteer to write one? :-))

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I think we should add two (or maybe just one) sub-chapters about FromStr and FromStrRadix, under the String chapter.

In any case, I think one should be able to find this example by searching for "conversion" or "convert" in the site searchbar.

[nixpulvis]

Would it be a good idea to have a "Basic Operation" chapter with sections on things like this and other very common functions? For example sqrt or to_string.

[abonander]

@nixpulvis I would put sqrt in a "Math Operations" chapter maybe. We should cover FromStr and to_string and casting e.g. int to f32 in a "Conversions" chapter.

[nixpulvis]

I like that, "Conversions" might make sense to go right after "Casting".

[maccoda]

@steveklabnik Just wanted to check did we need anything else to close this one off? 😄

[steveklabnik]

We're good!