feat(option): add flat

Author: glennsl

src/Core__Option.mjs

@@ -7,6 +7,13 @@ function some(value) {
   return Caml_option.some(value);
 }
 
+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))) {
@@ -112,6 +119,7 @@ function cmp(a, b, f) {
 
 export {
   some ,
+  flat ,
   filter ,
   forEach ,
   getExn ,

src/Core__Option.res

@@ -24,6 +24,12 @@
 
 let some = value => Some(value)
 
+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

@@ -51,6 +51,18 @@ Option.some("foo") // Some("foo")
 */
 let some: 'a => option<'a>
 
+/**
+`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`.