feat(option): add flat

Author: glennsl

src/Core__Option.mjs

@@ -3,6 +3,13 @@
 import * as Curry from "rescript/lib/es6/curry.js";
 import * as Caml_option from "rescript/lib/es6/caml_option.js";
 
+function flat(opt) {
+  if (opt !== undefined) {
+    return Caml_option.valFromOption(opt);
+  }
+  
+}
+
 function filter(opt, p) {
   var p$1 = Curry.__1(p);
   if (opt !== undefined && p$1(Caml_option.valFromOption(opt))) {
@@ -107,6 +114,7 @@ function cmp(a, b, f) {
 }
 
 export {
+  flat ,
   filter ,
   forEach ,
   getExn ,

src/Core__Option.res

@@ -22,6 +22,12 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
 
+let flat = opt =>
+  switch opt {
+  | Some(v) => v
+  | None => None
+  }
+
 let filterU = (opt, p) =>
   switch opt {
   | Some(x) as some if p(. x) => some

src/Core__Option.resi

@@ -39,6 +39,18 @@ let someString: option<string> = Some("hello")
 ```
 */
 
+/**
+`flat(value)` flattens a nested `option` value to a single level..
+
+## Examples
+
+```rescript
+Option.float(Some(Some(10))) // Some(10)
+Option.flat(Some(None)) // None
+```
+*/
+let flat: option<option<'a>> => option<'a>
+
 /**
 `filter(opt, f)` applies `f` to `opt`, if `f` returns `true`, then it returns `Some(value)`, otherwise returns `None`.