Merge pull request #1281 from illiteratewriter/closures-generics

Add reference to Generics

src/fn/closures/input_parameters.md

@@ -1,33 +1,34 @@
 # As input parameters
 
-While Rust chooses how to capture variables on the fly mostly without type 
-annotation, this ambiguity is not allowed when writing functions. When 
-taking a closure as an input parameter, the closure's complete type must be 
-annotated using one of a few `traits`. In order of decreasing restriction, 
+While Rust chooses how to capture variables on the fly mostly without type
+annotation, this ambiguity is not allowed when writing functions. When
+taking a closure as an input parameter, the closure's complete type must be
+annotated using one of a few `traits`. In order of decreasing restriction,
 they are:
 
 * `Fn`: the closure captures by reference (`&T`)
 * `FnMut`: the closure captures by mutable reference (`&mut T`)
 * `FnOnce`: the closure captures by value (`T`)
 
-On a variable-by-variable basis, the compiler will capture variables in the 
-least restrictive manner possible. 
+On a variable-by-variable basis, the compiler will capture variables in the
+least restrictive manner possible.
 
-For instance, consider a parameter annotated as `FnOnce`. This specifies 
-that the closure *may* capture by `&T`, `&mut T`, or `T`, but the compiler 
-will ultimately choose based on how the captured variables are used in the 
+For instance, consider a parameter annotated as `FnOnce`. This specifies
+that the closure *may* capture by `&T`, `&mut T`, or `T`, but the compiler
+will ultimately choose based on how the captured variables are used in the
 closure.
 
-This is because if a move is possible, then any type of borrow should also 
-be possible. Note that the reverse is not true. If the parameter is 
-annotated as `Fn`, then capturing variables by `&mut T` or `T` are not 
+This is because if a move is possible, then any type of borrow should also
+be possible. Note that the reverse is not true. If the parameter is
+annotated as `Fn`, then capturing variables by `&mut T` or `T` are not
 allowed.
 
-In the following example, try swapping the usage of `Fn`, `FnMut`, and 
+In the following example, try swapping the usage of `Fn`, `FnMut`, and
 `FnOnce` to see what happens:
 
 ```rust,editable
 // A function which takes a closure as an argument and calls it.
+// <F> denotes that F is a "Generic type parameter"
 fn apply<F>(f: F) where
     // The closure takes no input and returns nothing.
     F: FnOnce() {
@@ -81,9 +82,11 @@ fn main() {
 
 ### See also:
 
-[`std::mem::drop`][drop], [`Fn`][fn], [`FnMut`][fnmut], and [`FnOnce`][fnonce]
+[`std::mem::drop`][drop], [`Fn`][fn], [`FnMut`][fnmut], [Generics][generics], [where][where] and [`FnOnce`][fnonce]
 
 [drop]: https://doc.rust-lang.org/std/mem/fn.drop.html
 [fn]: https://doc.rust-lang.org/std/ops/trait.Fn.html
 [fnmut]: https://doc.rust-lang.org/std/ops/trait.FnMut.html
 [fnonce]: https://doc.rust-lang.org/std/ops/trait.FnOnce.html
+[generics]: ../../generics.md
+[where]: ../../generics/where.md