added functions unset and unset!

README.md

@@ -329,6 +329,8 @@ reverse | `(reverse [1 2 3])` | `[3 2 1]` | Reverse the order of a sequence. Use
 key?    | `(key? {"a" "b"} "a")` | `true` | Return true if the hash-map contains the given key.
 set     | `(set {"a" 1} "b" 2)` | `{"a":1 "b":2}` | Create new hash-map which contains the given key-value pair.
 set!    | `(set! {"a" 1} "b" 2)` | `2` | Modify the given hash-map by setting the given key-value pair and return the set value. **This function is mutable!**
+unset   | `(unset {"a":1 "b":2 "c":3} "b")` | `{"a":1 "c":3}` | Create a new hash-map with the given key removed.
+unset!  | `(unset! {"a":1 "b":2 "c":3} "b")` | `2` | Modify the given hash-map by removing the given key and return the corresponding value. **This function is mutable!**
 keys    | `(keys {"a" 1 "b" 2})` | `("a" "b")` | Return a list of the keys for a hash-map.
 values  | `(values {"a" 1 "b" 2})` | `(1 2)` | Return a list of the values for a hash-map.
 zip     | `(zip ["a" "b"] [1 2])` | `{"a":1 "b":2}` | Create a hash-map using the first sequence as keys and the second as values. Uses [array_combine](https://www.php.net/manual/en/function.array-combine.php) internally.

src/Hash.php

@@ -17,4 +17,15 @@ class Hash extends Collection
         $this->data[$key] = $value;
         return $value;
     }
+
+    public function unset(string $key)
+    {
+        if (array_key_exists($key, $this->data)) {
+            $value = $this->data[$key];
+            unset($this->data[$key]);
+            return $value;
+        }
+
+        return null;
+    }
 }

src/Lib/Collections.php

@@ -255,6 +255,20 @@ class Collections implements ILib
             }
         ));
 
+        $env->set('unset', new CoreFunc('unset', 'Create a new hash-map from the first argument with the given key removed.', 2, 2,
+            function (Hash $a, string $key) {
+                $data = $a->getData();
+                unset($data[$key]);
+                return new Hash($data);
+            }
+        ));
+
+        $env->set('unset!', new CoreFunc('unset!', 'Modify the hash-map (first argument) and remove the given key.', 2, 2,
+            function (Hash $a, string $key) {
+                return $a->unset($key);
+            }
+        ));
+
         $env->set('keys', new CoreFunc('keys', 'Return the keys of a hash-map as a list.', 1, 1,
             fn (Hash $a) => new MList(array_keys($a->getData()))
         ));