Remove inverse example from generics part of TRPL

Fixes #24325.

Author: steveklabnik

src/doc/trpl/generics.md

@@ -90,88 +90,3 @@ if we wanted to. Convention says that the first generic parameter should be
 
 The `Result<T, E>` type is intended to be used to return the result of a
 computation, and to have the ability to return an error if it didn't work out.
-Here's an example:
-
-```{rust}
-let x: Result<f64, String> = Ok(2.3f64);
-let y: Result<f64, String> = Err("There was an error.".to_string());
-```
-
-This particular Result will return an `f64` if there's a success, and a
-`String` if there's a failure. Let's write a function that uses `Result<T, E>`:
-
-```{rust}
-fn inverse(x: f64) -> Result<f64, String> {
-    if x == 0.0f64 { return Err("x cannot be zero!".to_string()); }
-
-    Ok(1.0f64 / x)
-}
-```
-
-We don't want to take the inverse of zero, so we check to make sure that we
-weren't passed zero. If we were, then we return an `Err`, with a message. If
-it's okay, we return an `Ok`, with the answer.
-
-Why does this matter? Well, remember how `match` does exhaustive matches?
-Here's how this function gets used:
-
-```{rust}
-# fn inverse(x: f64) -> Result<f64, String> {
-#     if x == 0.0f64 { return Err("x cannot be zero!".to_string()); }
-#     Ok(1.0f64 / x)
-# }
-let x = inverse(25.0f64);
-
-match x {
-    Ok(x) => println!("The inverse of 25 is {}", x),
-    Err(msg) => println!("Error: {}", msg),
-}
-```
-
-The `match` enforces that we handle the `Err` case. In addition, because the
-answer is wrapped up in an `Ok`, we can't just use the result without doing
-the match:
-
-```{rust,ignore}
-let x = inverse(25.0f64);
-println!("{}", x + 2.0f64); // error: binary operation `+` cannot be applied
-           // to type `core::result::Result<f64,collections::string::String>`
-```
-
-This function is great, but there's one other problem: it only works for 64 bit
-floating point values. What if we wanted to handle 32 bit floating point as
-well? We'd have to write this:
-
-```{rust}
-fn inverse32(x: f32) -> Result<f32, String> {
-    if x == 0.0f32 { return Err("x cannot be zero!".to_string()); }
-
-    Ok(1.0f32 / x)
-}
-```
-
-Bummer. What we need is a *generic function*. Luckily, we can write one!
-However, it won't _quite_ work yet. Before we get into that, let's talk syntax.
-A generic version of `inverse` would look something like this:
-
-```{rust,ignore}
-fn inverse<T>(x: T) -> Result<T, String> {
-    if x == 0.0 { return Err("x cannot be zero!".to_string()); }
-
-    Ok(1.0 / x)
-}
-```
-
-Just like how we had `Option<T>`, we use a similar syntax for `inverse<T>`.
-We can then use `T` inside the rest of the signature: `x` has type `T`, and half
-of the `Result` has type `T`. However, if we try to compile that example, we'll get
-an error:
-
-```text
-error: binary operation `==` cannot be applied to type `T`
-```
-
-Because `T` can be _any_ type, it may be a type that doesn't implement `==`,
-and therefore, the first line would be wrong. What do we do?
-
-To fix this example, we need to learn about another Rust feature: traits.