Add test

coconut/tests/src/cocotest/agnostic/suite.coco

@@ -1079,6 +1079,7 @@ forward 2""") == 900
     assert first_false_and_last_true([3, 2, 1, 0, "11", "1", ""]) == (0, "1")
     assert ret_args_kwargs ↤** dict(a=1) == ((), dict(a=1))
     assert ret_args_kwargs ↤**? None is None
+    assert [1, 2, 3] |> reduce_with_init$(+) == 6 == (1, 2, 3) |> iter |> reduce_with_init$((+), init=0)
 
     with process_map.multiple_sequential_calls():  # type: ignore
         assert process_map(tuple <.. (|>)$(to_sort), qsorts) |> list == [to_sort |> sorted |> tuple] * len(qsorts)

coconut/tests/src/cocotest/agnostic/util.coco

@@ -1686,7 +1686,7 @@ sum_evens = (
 )
 
 
-# n-ary reduction
+# reduction
 def binary_reduce(binop, it) = (
     it
     |> reiterable
@@ -1703,6 +1703,8 @@ def nary_reduce(n, op, it) = (
 
 binary_reduce_ = nary_reduce$(2)
 
+match def reduce_with_init(f, xs, init=type(xs[0])()) = reduce(f, xs, init)
+
 
 # last/end
 import operator