Use non deprecated functions in Chapter 2. Programming a Guessing Game

[TexanDoomGuy]

Chapter 2. Programming a Guessing Game uses thread_rng() and gen_range(), which are deprecated.
I replaced every thread_rng() with rng(), and every gen_range() with random_range()

The function is also referenced in a few other areas, of which I updated.

[Fnige]

Dont forget to update the rand version shown in the chapter too along with the cargo build output

[chriskrycho]

Thank you! I’ll take a look at this later this week as part of my work to prepare the book for the 2024 Edition release!

[chriskrycho]

These changes are solid—thank you! We need a few more to be able to land this:

1. A better title for this is “Update to use rand 0.9 throughout”. Those functions are not deprecated on the version that the book is using, after all!

2. We do indeed need to update all instances of rand = "0.8.5" to rand = "0.9.0" in the Cargo.toml files throughout.¹ That includes in the text immediately after including Listing 2-2, which itself shows adding rand to the Cargo.toml file.

   That will also flag up the need for some changes in Chapter 14!

3. We also need to update the sections Ensuring Reproducible Builds with the Cargo.lock File and Updating a Crate to Get a New Version in Ch. 2 to use 0.9.0 as the starting point and 0.9.1 and 0.10.0 as the “new versions” in the text, in the manual-regeneration comment, and in the code samples.

Footnotes

1. It’s quite surprising to me that this is passing CI at the moment! But that’s an issue with something about how we’re running mdbook test and not specific to this PR. I will follow up on that in parallel to our landing this. ↩