improve function.{curry2, .., curry6) docblocks

1 files changed, 57 insertions, 10 deletions

diff --git a/src/gleam/function.gleam b/src/gleam/function.gleam
index 312dfba..164a43c 100644
--- a/src/gleam/function.gleam
+++ b/src/gleam/function.gleam
@@ -5,37 +5,84 @@ pub fn compose(fun1: fn(a) -> b, fun2: fn(b) -> c) -> fn(a) -> c {
   fn(a) { fun2(fun1(a)) }
 }
 
-/// Takes a function with arity two
-/// and returns a curried equivalent:
+/// Takes a function with `2` arguments (an arity of `2`), and returns the
+/// curried equivalent.
+///
 /// `fn(a, b) -> c` becomes `fn(a) -> fn(b) -> c`.
 ///
+/// ## Examples
+///
+/// *Currying* creates a new function that is identical to the given function
+/// except that arguments must now be supplied one by one over several function
+/// calls. It thus is the process of taking a function with `n` arguments
+/// and producing a sequence of `n` single-argument functions. Given:
+///
+/// ```gleam
+/// > fn my_fun(i: Int, s: String) -> String { ... }
+/// ```
+///
+/// …calling `curry2(my_fun)` would return the curried equivalent, like so:
+///
+/// ```gleam
+/// > curry2(my_fun)
+/// fn(Int) -> fn(String) -> String
+/// ```
+///
+/// Currying is useful when you want to partially apply a function with
+/// some arguments and then pass it somewhere else, for example:
+///
+/// ```gleam
+/// > import gleam/list
+/// > let multiply = curry2(fn(x, y) { x * y })
+/// > let doubles = list.map([1, 2, 3], multiply(2))
+/// [2, 4, 6]
+/// ```
+///
 pub fn curry2(fun: fn(a, b) -> value) {
   fn(a) { fn(b) { fun(a, b) } }
 }
 
-/// Takes a function with arity three
-/// and returns a curried equivalent:
+/// Takes a function with `3` arguments (an arity of `3`), and returns the
+/// curried equivalent.
+///
 /// `fn(a, b, c) -> d` becomes `fn(a) -> fn(b) -> fn(c) -> d`.
 ///
+/// See [`curry2`](#curry2) for a detailed explanation.
+///
 pub fn curry3(fun: fn(a, b, c) -> value) {
   fn(a) { fn(b) { fn(c) { fun(a, b, c) } } }
 }
 
-/// Takes a function with arity four
-/// and returns a curried equivalent.
+/// Takes a function with `4` arguments (an arity of `4`), and returns the
+/// curried equivalent.
+///
+/// `fn(a, b, c, d) -> e` becomes `fn(a) -> fn(b) -> fn(c) -> fn(d) -> e`.
+///
+/// See [`curry2`](#curry2) for a detailed explanation.
 ///
 pub fn curry4(fun: fn(a, b, c, d) -> value) {
   fn(a) { fn(b) { fn(c) { fn(d) { fun(a, b, c, d) } } } }
 }
 
-/// Takes a function with arity five
-/// and returns a curried equivalent.
+/// Takes a function with `5` arguments (an arity of `5`), and returns the
+/// curried equivalent.
+///
+/// `fn(a, b, c, d, e) -> f` becomes
+/// `fn(a) -> fn(b) -> fn(c) -> fn(d) -> fn(e) -> f`.
+///
+/// See [`curry2`](#curry2) for a detailed explanation.
+///
 pub fn curry5(fun: fn(a, b, c, d, e) -> value) {
   fn(a) { fn(b) { fn(c) { fn(d) { fn(e) { fun(a, b, c, d, e) } } } } }
 }
 
-/// Takes a function with arity six
-/// and returns a curried equivalent.
+/// Takes a function with `6` arguments (an arity of `6`), and returns the
+/// curried equivalent.
+///
+/// `fn(a, b, c, d, e, f) -> g` becomes
+/// `fn(a) -> fn(b) -> fn(c) -> fn(d) -> fn(e) -> fn(f) -> g`.
+///
+/// See [`curry2`](#curry2) for a detailed explanation.
 ///
 pub fn curry6(fun: fn(a, b, c, d, e, f) -> value) {
   fn(a) {