Fast monadic transpose

1 files changed, 6 insertions, 3 deletions

diff --git a/src/r.bqn b/src/r.bqn
index 0bfd5da4..d153a53d 100644
--- a/src/r.bqn
+++ b/src/r.bqn
@@ -31,6 +31,7 @@ _fold←{
 ToArray ← <⍟(1-IsArray)
 Int←IsArray◶⟨⌊⊸=,0⟩
 Nat←IsArray◶⟨0⊸≤×⌊⊸=,0⟩
+Cell←{(𝕨⊸+⊑𝕩˜)⌜↕(≠𝕩)-𝕨}⟜≢
 
 ∾ ← {k←≠𝕨⋄k⊸≤◶⟨⊑⟜𝕨⋄-⟜k⊑𝕩˜⟩⌜↕k+≠𝕩}  # LIMITED to two vector arguments
 
@@ -96,6 +97,11 @@ Indices←{
   }⍟(0<l)𝕩
 }
 
+Transpose←{
+  l←≠𝕩 ⋄ m←1×´c←1 Cell 𝕩
+  (c⥊↕m)(+⟜(m⊸×)⊑(⥊𝕩)˜)⌜↕l
+}⍟(0<=)
+
 _under_←{
   i←↕l←1×´s←≢𝕩
   v←⥊𝕨𝔽○𝔾𝕩
@@ -174,8 +180,6 @@ Depth←IsArray◶0‿{1+0⌈´Depth⌜⥊𝕩}
 ≢ ↩ ≢              ⊘ (¬Match)
 
 
-DropV← {⊑⟜𝕩⌜𝕨+↕𝕨-˜≠𝕩}
-Cell ← DropV⟜≢
 Pair ← {⟨𝕩⟩} ⊘ {⟨𝕨,𝕩⟩}
 
 Merge←{
@@ -352,7 +356,6 @@ ReorderAxes←{
   𝕨↩𝕨∾𝕨(¬∘∊˜/⊢)↕r
   (𝕨⊸⊏Pick𝕩˜)⌜↕⌊´⌜𝕨⊔≢𝕩
 }
-Transpose←(=-1˜)⊸ReorderAxes⍟(0<=)
 ⍉ ← Transpose      ⊘ ReorderAxes
 
 # Sorting