Add reset-vals! and swap-vals! for atoms (#399)

Author: chrisrink10

src/basilisp/core.lpy

@@ -714,12 +714,37 @@
       v
       (recur atom v))))
 
+(defn reset-vals!
+  "Reset the value of an atom to v without regard to the previous value.
+  Return a vector containing the new value and the old value in that order."
+  [atom v]
+  (let [current (deref atom)]
+    (if (compare-and-set! atom current v)
+      [v current]
+      (recur atom v))))
+
 (defn swap!
   "Atomically swap the value of an atom to the return value of (apply f
   current-value args). The function f may be called multiple times while
   swapping, so should be free of side effects. Return the new value."
   [atom f & args]
-  (apply basilisp.lang.runtime/swap atom f args))
+  (let [current (deref atom)
+        new-val (apply f current args)]
+    (if (compare-and-set! atom current new-val)
+      new-val
+      (recur atom f args))) )
+
+(defn swap-vals!
+  "Atomically swap the value of an atom to the return value of (apply f
+  current-value args). The function f may be called multiple times while
+  swapping, so should be free of side effects. Return a vector containing
+  the new value and the old value in that order."
+  [atom f & args]
+  (let [current (deref atom)
+        new-val (apply f current args)]
+    (if (compare-and-set! atom current new-val)
+      [new-val current]
+      (recur atom f args))))
 
 (defn atom
   "Return an Atom containing v. The value of an Atom at any point in time

src/basilisp/lang/runtime.py

@@ -934,13 +934,6 @@ def deref(o, timeout_s=None, timeout_val=None):
     raise TypeError(f"Object of type {type(o)} cannot be dereferenced")
 
 
-def swap(a: Atom, f, *args):
-    """Atomically swap the value of an atom to the return value of (apply f
-    current-value args). The function f may be called multiple times while
-    swapping, so should be free of side effects. Return the new value."""
-    return a.swap(f, *args)
-
-
 def equals(v1, v2) -> bool:
     """Compare two objects by value. Unlike the standard Python equality operator,
     this function does not consider 1 == True or 0 == False. All other equality

tests/basilisp/runtime_test.py

@@ -270,16 +270,6 @@ def test_deref():
         runtime.deref(vec.Vector.empty())
 
 
-def test_swap():
-    assert 3 == runtime.swap(atom.Atom(1), lambda x, y: x + y, 2)
-    assert vec.v(1) == runtime.swap(
-        atom.Atom(vec.Vector.empty()), lambda v, e: v.cons(e), 1
-    )
-
-    with pytest.raises(AttributeError):
-        runtime.swap(1, lambda x, y: x + y, 2)
-
-
 class TestToPython:
     def test_literal_to_py(self):
         assert None is runtime.to_py(None)