Depth-1 structural Under implementation

1 files changed, 7 insertions, 0 deletions

diff --git a/impl.bqn b/impl.bqn
index 558ef06b..2285f66e 100644
--- a/impl.bqn
+++ b/impl.bqn
@@ -416,3 +416,10 @@ _repeat_←{
   (|⊑<⟜0⊑pos‿neg˜)⚇0 n
 }
 ⍟ ↩ _repeat_
+
+_under_←{
+  i←↕×´s←≢𝕩
+  v←⥊𝕨𝔽○𝔾𝕩⋄gi←⥊𝔾s⥊i⋄k←¬i∊gi
+  s⥊(⍋(/k)∾gi)⊏(k/⥊𝕩)∾v
+}
+⌾ ← _under_