Adding missing find function, fixes #564

SUMMARY.md

@@ -113,6 +113,7 @@
   * [concat](appendix_c.md#concat)
   * [eq](appendix_c.md#eq)
   * [filter](appendix_c.md#filter)
+  * [find](appendix_c.md#find)
   * [flip](appendix_c.md#flip)
   * [forEach](appendix_c.md#foreach)
   * [head](appendix_c.md#head)

appendix_c.md

@@ -10,7 +10,7 @@ In order to find functions that are more production-ready, have a peek at
 
 Note that functions refer to the `curry` & `compose` functions defined in [Appendix A](./appendix_a.md)
 
-## add 
+## add
 
 ```js
 // add :: Number -> Number -> Number
@@ -52,14 +52,21 @@ const eq = curry((a, b) => a === b);
 const filter = curry((fn, xs) => xs.filter(fn));
 ```
 
+## find
+
+```js
+// find :: (a -> Boolean) -> [a] -> a
+const find = curry((fn, list) => list.find(fn))
+```
+
 ## flip
 
 ```js
 // flip :: (a -> b -> c) -> b -> a -> c
 const flip = curry((fn, a, b) => fn(b, a));
 ```
 
-## forEach 
+## forEach
 
 ```js
 // forEach :: (a -> ()) -> [a] -> ()
@@ -108,7 +115,7 @@ const map = curry((fn, f) => f.map(fn));
 const match = curry((re, str) => re.test(str));
 ```
 
-## prop 
+## prop
 
 ```js
 // prop :: String -> Object -> a

exercises/support.js

@@ -559,7 +559,7 @@ class Task {
   }
 }
 
-// In nodejs the existance of a class method named `inspect` will trigger a deprecation warning
+// In nodejs the existence of a class method named `inspect` will trigger a deprecation warning
 // when passing an instance to `console.log`:
 // `(node:3845) [DEP0079] DeprecationWarning: Custom inspection function on Objects via .inspect() is deprecated`
 // The solution is to alias the existing inspect method with the special inspect symbol exported by node
@@ -724,6 +724,15 @@ const filter = curry(function filter(fn, xs) {
   return xs.filter(fn);
 });
 
+const find = curry(function find(fn, xs) {
+  assert(
+    typeof fn === 'function' && Array.isArray(xs),
+    typeMismatch('(a -> Boolean) -> [a] -> a', [getType(fn), getType(xs), getType(xs)].join(' -> '), 'find'),
+  );
+
+  return xs.find(fn);
+});
+
 const flip = curry(function flip(fn, a, b) {
   assert(
     typeof fn === 'function',
@@ -1071,6 +1080,7 @@ if (typeof module === 'object') {
     concat,
     eq,
     filter,
+    find,
     flip,
     forEach,
     head,