%% syntaxe : A B addm --> A+B  (nouvelle matrice)
/addm {
9 dict begin
   /B exch def
   /A exch def
%%   B dimmatrix /n' exch def /m' exch def
   A dimmatrix /n exch def /m exch def
   /M m n newmatrix def
   /i 0 def
   m {
      /j 0 def
      n {
   	 M i j 
   	    A i j get_ij B i j get_ij add 
   	 put_ij
   	 /j j 1 add store 
      } repeat
   /i i 1 add store
   } repeat
   M
end
} def