From fa3a407253907ea754ac813d7ab3efd788d78778 Mon Sep 17 00:00:00 2001
From: Pierre-Francois Loos <pierrefrancois.loos@gmail.com>
Date: Mon, 12 Oct 2020 08:57:00 +0200
Subject: [PATCH] Add Multipole.to_file

---
 dune-project                         |  1 -
 gaussian_integrals/lib/multipole.ml  | 16 ++++++++++++++++
 gaussian_integrals/lib/multipole.mli |  4 ++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/dune-project b/dune-project
index 3d7638a..74b9906 100644
--- a/dune-project
+++ b/dune-project
@@ -27,7 +27,6 @@ in quantum chemistry.")
   (depends
     (ocaml (>= 4.10))
     (dune  (>= 1.10))
-    str
     lacaml
     getopt
     zarith
diff --git a/gaussian_integrals/lib/multipole.ml b/gaussian_integrals/lib/multipole.ml
index deea6e0..83cfe40 100644
--- a/gaussian_integrals/lib/multipole.ml
+++ b/gaussian_integrals/lib/multipole.ml
@@ -222,3 +222,19 @@ let of_basis basis =
   Array.iter Matrix.detri_inplace result;
   result
 
+
+let to_file ~filename eni_array =
+  let n = Matrix.dim1 eni_array in
+  let eni_array = Matrix.to_bigarray_inplace eni_array in
+  let oc = open_out filename in
+    
+  for j=1 to n do
+    for i=1 to j do
+      let value = eni_array.{i,j} in
+      if (value <> 0.) then
+        Printf.fprintf oc " %5d %5d %20.15f\n" i j value;
+    done;
+  done;
+  close_out oc
+    
+
diff --git a/gaussian_integrals/lib/multipole.mli b/gaussian_integrals/lib/multipole.mli
index f9e8ba8..f897ccc 100644
--- a/gaussian_integrals/lib/multipole.mli
+++ b/gaussian_integrals/lib/multipole.mli
@@ -60,3 +60,7 @@ val matrix_z4 : t -> (Basis.t, Basis.t) Matrix.t
 (** {% $$ \langle \chi_i | z^4 | \chi_j \rangle $$ %} *)
 
 val of_basis : Basis.t -> t
+
+val to_file : filename:string -> (Basis.t, Basis.t) Matrix.t -> unit                                                
+(** Write a matrix to a file *)
+