From 687474fed294cdf379628286bc26591c3db88dd2 Mon Sep 17 00:00:00 2001
From: Jiri Pittner <jiri@pittnerovi.com>
Date: Mon, 10 Nov 2025 22:02:07 +0100
Subject: [PATCH] tensor: index names in merge_indices

---
 t.cc      | 9 +++++----
 tensor.cc | 1 +
 tensor.h  | 4 ++++
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/t.cc b/t.cc
index 2408964..f01b2e0 100644
--- a/t.cc
+++ b/t.cc
@@ -4048,16 +4048,17 @@ NRVec<INDEXGROUP> shape(3);
 
 
 Tensor<double> x(shape); x.randomize(1.);
-cout <<"x= "<<x.shape;
+x.defaultnames();
+cout <<"x= "<<x.shape << " "<<x.names<<endl;
 Tensor<double> xf=x.flatten(1);
-cout <<"xf= "<<xf.shape;
+cout <<"xf= "<<xf.shape << " "<<xf.names<<endl;
 Tensor<double> xxx=x.unwind_index_group(1);
-cout <<"xxx= "<<xxx.shape<<endl;
+cout <<"xxx= "<<xxx.shape<<" "<<xxx.names<<endl;
 
 INDEXLIST il(r);
 for(int i=0; i<r; ++i) il[i]= {1+i,0};
 Tensor<double> xx = xf.merge_indices(il,sym);
-cout <<"xx = "<<xx.shape;
+cout <<"xx = "<<xx.shape<< " "<<xx.names<<endl;
 cout <<"Error = "<<(xx-xxx).norm()<<endl;
 
 }
diff --git a/tensor.cc b/tensor.cc
index 806c9d5..efc873f 100644
--- a/tensor.cc
+++ b/tensor.cc
@@ -1746,6 +1746,7 @@ else
 
 Tensor<T> r(newshape);
 r.apply_permutation_algebra(*this,pa,false,(T)1/(T)pa.size(),0);
+if(is_named()) r.names=names.permuted(basicperm,true);	
 return r;
 }
 
diff --git a/tensor.h b/tensor.h
index a23c498..357146a 100644
--- a/tensor.h
+++ b/tensor.h
@@ -132,6 +132,10 @@ bool upperindex;
 std::ostream & operator<<(std::ostream &s, const INDEXGROUP &x);
 std::istream & operator>>(std::istream &s, INDEXGROUP &x);
 
+std::ostream & operator<<(std::ostream &s, const INDEXNAME &x);
+std::istream & operator>>(std::istream &s, INDEXNAME &x);
+
+
 
 
 template<>