Merge pull request #5442 from nkrkv/sync-belt-doc-headers-js-option

Sync docs for js_option.ml

Author: ryyppy

jscomp/others/js_option.ml

@@ -22,29 +22,85 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)
 
+(** Provide utilities for handling `option`. *)
+
+(**
+  `Js.Option.t` is an alias for `option`
+*)
 type 'a t = 'a option
 
+(**
+  Wraps the given value in `Some()`
+
+  ```res example
+  Js.Option.some(1066) == Some(1066)
+  ```
+*)
 let some x = Some x 
 
+(**
+  Returns `true` if the argument is `Some(value)`; `false` if the argument is
+  `None`.
+*)
 let isSome = function
   | None -> false
   | Some _ -> true
 
+(**
+  The first argument to `isSomeValue` is an uncurried function `eq()` that
+  takes two arguments and returns `true` if they are considered to be equal. It
+  is used to compare a plain value `v1`(the second argument) with an `option`
+  value. If the `option` value is `None`, `isSomeValue()` returns `false`; if
+  the third argument is `Some(v2)`, `isSomeValue()` returns the result of
+  calling `eq(v1, v2)`.
+
+  ```res example
+  let clockEqual = (. a, b) => mod(a, 12) == mod(b, 12)
+  Js.Option.isSomeValue(clockEqual, 3, Some(15)) == true
+  Js.Option.isSomeValue(clockEqual, 3, Some(4)) == false
+  Js.Option.isSomeValue(clockEqual, 3, None) == false
+  ```
+*)
 let isSomeValue eq v x =
   match x with 
   | None -> false 
   | Some x -> eq v x [@bs]
 
-
+(** Returns `true` if the argument is `None`; `false` otherwise. *)
 let isNone = function
   | None -> true
   | Some _ -> false
 
+(**
+  If the argument to `getExn()` is of the form `Some(value)`, returns `value`.
+  If given `None`, it throws a `getExn` exception.
+*)
 let getExn x =
   match x with 
   | None -> Js_exn.raiseError "getExn"
   | Some x -> x 
 
+(**
+  The first argument to `equal` is an uncurried function `eq()` that takes two
+  arguments and returns `true` if they are considered to be equal. The second
+and third arguments are `option` values.
+
+  If the second and third arguments are of the form:
+
+  * `Some(v1)` and `Some(v2)`: returns `eq(v1, v2)`
+  * `Some(v1)` and `None`: returns `false`
+  * `None` and `Some(v2)`: returns `false`
+  * `None` and `None`: returns `true`
+
+  ```res example
+  let clockEqual = (. a, b) => mod(a, 12) == mod(b, 12)
+  Js.Option.equal(clockEqual, Some(3), Some(15)) == true
+  Js.Option.equal(clockEqual, Some(3), Some(16)) == false
+  Js.Option.equal(clockEqual, Some(3), None) == false
+  Js.Option.equal(clockEqual, None, Some(15)) == false
+  Js.Option.equal(clockEqual, None, None) == true
+  ```
+*)
 let equal eq a b =
   match a  with 
   | None -> b = None 
@@ -54,23 +110,73 @@ let equal eq a b =
     | Some y -> eq x y [@bs]
     end
 
+(**
+  The first argument to `andThen()` is an uncurried function `f()` that takes a
+  plain value and returns an `option` result. The second argument is an
+  `option` value. If the second argument is `None`, the return value is `None`.
+  If the second argument is `Some(v)`, the return value is `f(v)`.
+
+  ```res example
+  let reciprocal = (. x) => x == 0 ? None : Some(1.0 /. Belt.Int.toFloat(x))
+  Js.Option.andThen(reciprocal, Some(5)) == Some(0.2)
+  Js.Option.andThen(reciprocal, Some(0)) == None
+  Js.Option.andThen(reciprocal, None) == None
+  ```
+*)
 let andThen f x =
   match x with 
   | None -> None 
   | Some x -> f x [@bs]
 
+(**
+  The first argument to `map()` is an uncurried function `f()` that takes a
+  plain value and returns a plain result. The second argument is an `option`
+  value. If it is of the form `Some(v)`, `map()` returns `Some(f(v))`; if it is
+  `None`, the return value is `None`, and function `f()` is not called.
+
+  ```res example
+  let square = (. x) => x * x
+  Js.Option.map(square, Some(3)) == Some(9)
+  Js.Option.map(square, None) == None
+  ```
+*)
 let map f x =
   match x with
   | None -> None
   | Some x -> Some (f x [@bs])
 
+(**
+  The first argument to `getWithDefault()` is a default value. If the second
+  argument is of the form `Some(v)`, `getWithDefault()` returns `v`; if the
+  second argument is `None`, the return value is the default value.
+
+  ```res example
+  Js.Option.getWithDefault(1066, Some(15)) == 15
+  Js.Option.getWithDefault(1066, None) == 1066
+  ```
+*)
 let getWithDefault a x =
   match x with
   | None -> a
   | Some x -> x
 
+(** **See:** [getWithDefault](#getWithDefault) *)
 let default = getWithDefault  
 
+(**
+  The first argument to `filter()` is an uncurried function that takes a plain
+  value and returns a boolean. The second argument is an `option` value.
+
+  If the second argument is of the form `Some(v)` and `f(v)` is `true`,
+  the return value is `Some(v)`. Otherwise, the return value is `None`.
+
+  ```res example
+  let isEven = (. x) => mod(x, 2) == 0
+  Js.Option.filter(isEven, Some(2)) == Some(2)
+  Js.Option.filter(isEven, Some(3)) == None
+  Js.Option.filter(isEven, None) == None
+  ```
+*)
 let filter f x =
   match x with
   | None -> None
@@ -80,6 +186,16 @@ let filter f x =
     else
       None
 
+(**
+  The `firstSome()` function takes two `option` values; if the first is of the form `Some(v1)`, that is the return value. Otherwise, `firstSome()` returns the second value.
+
+  ```res example
+  Js.Option.firstSome(Some("one"), Some("two")) == Some("one")
+  Js.Option.firstSome(Some("one"), None) == Some("one")
+  Js.Option.firstSome(None, Some("two")) == Some("two")
+  Js.Option.firstSome(None, None) == None
+  ```
+*)
 let firstSome a b =
   match (a, b) with
   | (Some _, _) -> a