Add the contains* function

README.md

@@ -34,6 +34,7 @@ Contains functions to handle Pact lists.
 * ```(defun enforce-list-bounds:bool (x:list idx:integer)``` : Verify and enforce that *idx* is in list bounds
 * ```(defun chain:list (in:list)``` : Chain list of lists
 * ```(defun enumerate-list:[object] (in:list)``` : Returns a list of objects {'i:idx, 'v:value} where i is the index, and v the value
+* ```(defun contains*:bool (in:list item)``` : Starred version of contains for list => arguments inverted
 * ```(defun first (in:list)``` : Returns the first item of a list
 * ```(defun last (in:list)``` : Returns the last item of the list
 * ```(defun at* (in:list idx:integer default)```: Returns the element at *idx*, but returns *default* if the list is too short

docs/source/util-lists.rst

@@ -72,6 +72,24 @@ Return a list of objects ``{'i:idx, 'v:value}`` where *'i* is the index, and *'v
   pact> (enumerate-list ["a", "b", "c"])
   [{"i": 0,"v": "a"} {"i": 1,"v": "b"} {"i": 2,"v": "c"}]
 
+
+contains*
+~~~~~~~~~
+*in* ``[<a>]`` *item* ``<a>`` *→* ``bool``
+
+Starred version of contains for list => arguments inverted.
+
+Useful for mapping and filtering
+
+.. code:: lisp
+
+  pact> (contains* ["a", "b", "c"] "c")
+  true
+
+  pact> (contains* ["a", "b", "c"] "d")
+  false
+
+
 first
 ~~~~~
 *in* ``[<a>]`` *→* ``<a>``

pact/contracts/util-lists.pact

@@ -44,6 +44,11 @@
       (zip (lambda (idx:integer x) {'i:idx, 'v:x}) indexes in))
   )
 
+  (defun contains*:bool (in:list item)
+    "Starred version of contains for list => arguments inverted"
+    (contains item in)
+  )
+
   ;; Getter Functions
   (defun first (in:list)
     "Returns the first item of a list"

pact/tests_repl/util-lists-test.repl

@@ -21,6 +21,10 @@
 (expect-that "Enumerated single element list" (= [{'i:0,'v:"a"}]) (enumerate-list ["a"]))
 (expect-that "Enumerated empty list" (= []) (enumerate-list []))
 
+;contains*
+(expect "List contains the element" true (contains* ["a", "b", "c"] "b"))
+(expect "List does not contain the element" false (contains* ["a", "b", "c"] "d"))
+
 ; first
 (expect-failure "Empty list must fail" "empty" (first []))
 (expect-that "First item is a " (= "a") (first ["a", "b", "c", "d"]))