From 7edc64cb198ef3a3e171570d761cc0cd8e5709ca Mon Sep 17 00:00:00 2001
From: hyrodium <hyrodium@gmail.com>
Date: Sat, 11 Nov 2023 15:46:54 +0900
Subject: [PATCH] add __changebasis_I_old to fix around NaN

---
 src/_ChangeBasis.jl | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/_ChangeBasis.jl b/src/_ChangeBasis.jl
index fc0e75072..ecf2dbe0e 100644
--- a/src/_ChangeBasis.jl
+++ b/src/_ChangeBasis.jl
@@ -395,11 +395,20 @@ function _changebasis_I_old(P::BSplineSpace{p,T}, P′::BSplineSpace{p′,T′})
     return A
 end
 
+function __changebasis_I_old(P1, P2)
+    _P1 = _degeneratize_I(P1)
+    _P2 = _degeneratize_I(P2)
+    A = _changebasis_I_old(P1,P2)
+    _A = zero(A)
+    _A[isnondegenerate_I.(P1,1:dim(P1)), isnondegenerate_I.(P2,1:dim(P2))] = _changebasis_I_old(_P1,_P2)
+    return _A
+end
+
 function _find_j_range_I(P::BSplineSpace{p}, P′::BSplineSpace{p′}, i, j_begin, j_end) where {p, p′}
     # TODO: avoid `_changebasis_I_old`
     # TODO: fix performance https://github.com/hyrodium/BasicBSpline.jl/pull/323#issuecomment-1723216566
     # TODO: remove threshold such as 1e-14
-    Aᵖ_old = _changebasis_I_old(P,P′)
+    Aᵖ_old = __changebasis_I_old(P,P′)
     j_begin = findfirst(e->abs(e)>1e-14, Aᵖ_old[i, :])
     j_end = findlast(e->abs(e)>1e-14, Aᵖ_old[i, :])
     return j_begin:j_end