Add uniquify by function overload to ε

Not inspired by a recent code golf challenge totally not.

documents/knowledge/elements.yaml

@@ -670,7 +670,7 @@
   vectorise: true
   tests:
     - '[["abc", "defg", "h"]] : [3, 4, 1]'
-    - '[[[1, 2, 3], [4], [5, 6, 7, 8]]] : [3, 1, 4]'
+    - "[[[1, 2, 3], [4], [5, 6, 7, 8]]] : [3, 1, 4]"
 
 - element: "¨@"
   name: Function Call / Declaration
@@ -2146,14 +2146,15 @@
     - '[[1, 22, 333]] : "  3\n 23\n123"'
     - '[[]] : ""'
 - element: "ε"
-  name: Absolute Difference / Repeat / Regex match
+  name: Absolute Difference / Repeat / Regex match / Uniquify by Function
   arity: 2
-  description: Returns the absolute difference / Fills an array of a certain length / Does a regex match
+  description: Returns the absolute difference / Fills an array of a certain length / Does a regex match / Uniquify by function
   overloads:
     num-num: abs(a - b)
     num-str: "[b] * a"
     str-num: "[a] * b"
     str-str: regex.match(b, a) (first match of regex b on a)
+    any-fun: keep only unique elements of a, where f(x) is unique
   vectorise: false
   tests:
     - "[5, 1] : 4"
@@ -5713,13 +5714,13 @@
   description: Diagonals of a matrix, starting with the shortest top diagonal
   arity: 1
   overloads:
-      lst: diagonals of a, starting with the shortest top diagonal
+    lst: diagonals of a, starting with the shortest top diagonal
   vectorise: false
   tests:
-      - "[[[1,2,3],[4,5,6],[7,8,9]]] : [[3], [2, 6], [1, 5, 9], [4, 8], [7]]"
-      - "[[[1,2,3,4],[5,6,7,8],[9,10,11,12]]] : [[4], [3, 8], [2, 7, 12], [1, 6, 11], [5, 10], [9]]"
-      - "[[[1,2,3],[4,5,6],[7,8,9],[10,11,12]]] : [[3], [2, 6], [1, 5, 9], [4, 8, 12], [7, 11], [10]]"
-      - "[[[]]] : []"
+    - "[[[1,2,3],[4,5,6],[7,8,9]]] : [[3], [2, 6], [1, 5, 9], [4, 8], [7]]"
+    - "[[[1,2,3,4],[5,6,7,8],[9,10,11,12]]] : [[4], [3, 8], [2, 7, 12], [1, 6, 11], [5, 10], [9]]"
+    - "[[[1,2,3],[4,5,6],[7,8,9],[10,11,12]]] : [[3], [2, 6], [1, 5, 9], [4, 8, 12], [7, 11], [10]]"
+    - "[[[]]] : []"
 
 - element: "Þḋ"
   name: Anti-diagonals
@@ -5739,14 +5740,14 @@
   description: Anti-diagonals of a matrix, starting with the shortest top anti-diagonal
   arity: 1
   overloads:
-      lst: anti-diagonals of a, starting with the shortest top anti-diagonal
+    lst: anti-diagonals of a, starting with the shortest top anti-diagonal
   vectorise: false
   tests:
-      - "[[[1,2,3],[4,5,6],[7,8,9]]] : [[1], [2, 4], [3, 5, 7], [6, 8], [9]]"
-      - "[[[1,2,3,4],[5,6,7,8],[9,10,11,12]]] : [[1], [2, 5], [3, 6, 9], [4, 7, 10], [8, 11], [12]]"
-      - "[[[1,2,3],[4,5,6],[7,8,9],[10,11,12]]] : [[1], [2, 4], [3, 5, 7], [6, 8, 10], [9, 11], [12]]"
-      - "[[[1,2,3],[4],[7,8,9]]] : [[1], [2, 4], [3, 7], [8], [9]]"
-      - "[[[]]] : []"
+    - "[[[1,2,3],[4,5,6],[7,8,9]]] : [[1], [2, 4], [3, 5, 7], [6, 8], [9]]"
+    - "[[[1,2,3,4],[5,6,7,8],[9,10,11,12]]] : [[1], [2, 5], [3, 6, 9], [4, 7, 10], [8, 11], [12]]"
+    - "[[[1,2,3],[4,5,6],[7,8,9],[10,11,12]]] : [[1], [2, 4], [3, 5, 7], [6, 8, 10], [9, 11], [12]]"
+    - "[[[1,2,3],[4],[7,8,9]]] : [[1], [2, 4], [3, 7], [8], [9]]"
+    - "[[[]]] : []"
 
 - element: "ÞS"
   name: Sublists
@@ -6373,7 +6374,6 @@
     - "[[]] : []"
     - "[[8,8,8,8,8,8,6,6,6,6,6,8,8,8,8,8,3,3]] : [[16, 17], [6, 7, 8, 9, 10], [0, 1, 2, 3, 4, 5, 11, 12, 13, 14, 15]]"
 
-
 - element: "Þ‟"
   name: List from Anti-Diagonals
   description: List of lists from anti-diagonals of a list
@@ -6384,7 +6384,6 @@
   tests:
     - "[[[1], [2, 6], [3, 7, 11], [4, 8, 12, 16], [5, 9, 13, 17, 21], [10, 14, 18, 22], [15, 19, 23], [20, 24], [25]]] : [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20], [21, 22, 23, 24, 25]]"
 
-
 - element: "Þ„"
   name: List from Diagonals
   description: List of lists from diagonals of a list

tests/test_complex.py

@@ -957,6 +957,16 @@ def test_if_modifier():
     assert stack[-1] == [1]
 
 
+def test_uniquify_by_function():
+    stack = run_vyxal("1 10 ṡ ⁽∷ ε")
+    assert stack[-1] == [1, 2]
+
+    stack = run_vyxal(
+        "`abc kfjhdg smdfb n dkfjf mnd weiqwop j wkej qkej madma` ⌈⁽Lε"
+    )
+    assert stack[-1] == ["abc", "kfjhdg", "smdfb", "n", "weiqwop", "wkej"]
+
+
 def test_set_intersect():
     stack = run_vyxal("Þ∞:↔")
     assert stack[-1][:10] == [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

vyxal/elements.py

@@ -463,8 +463,27 @@ def absolute_difference(lhs, rhs, ctx):
     (num, str) -> Array of length a filled with b
     (str, num) -> Array of length b filled with a
     (str, str) -> single regex match of b against a
+    (lst, fun) -> unique list of results of applying fun to each element of lst
     """
     ts = vy_type(lhs, rhs)
+    if types.FunctionType in ts:
+        # Uniquify by function result
+        lst, fun = (
+            (lhs, rhs) if isinstance(rhs, types.FunctionType) else (rhs, lhs)
+        )
+        lst = iterable(lst, ctx)
+
+        @lazylist_from(lst)
+        def gen():
+            seen = set()
+            for item in lst:
+                res = safe_apply(fun, item, ctx=ctx)
+                if res not in seen:
+                    seen.add(res)
+                    yield item
+
+        return gen()
+
     return {
         (NUMBER_TYPE, NUMBER_TYPE): lambda: abs(lhs - rhs),
         (NUMBER_TYPE, str): lambda: [rhs] * lhs,