A=testmatrix('magi',3) /// \sleftarrow{{\normalfont a \verb+3x3+ magic square}}
[ma,na]=size(A); /// \sleftarrow{{\normalfont size of the string matrix}}
B=string(A) /// \sleftarrow{{\normalfont from scalar matrix to string matrix}}
delim='\BS\BS';  
B=[B,delim(ones(ma,1))]; /// \sleftarrow{{\normalfont adding a column}}
///{\normalfont  note that \verb+delim(ones(ma,1))+ builds a \verb+(ma,1)+ with string \verb+delim+ in each row}
B=strcat(B',' & ') ///  \sleftarrow{{\normalfont transpose and concatenate with a separator}}
B=strsubst(B,'& \BS\BS &','\BS\BS') ///  \sleftarrow{{\normalfont substitutions }}
B=strsubst(B,'& \BS\BS','') ///  \sleftarrow{{\normalfont \verb+B+ is now a string}}

delim="c";delim=strcat(delim(ones(na,1))) /// \sleftarrow{{\normalfont builds a repeated pattern (\verb+na+ times)}}

text=['\BS[ A= {\BS}begin\{array\}\{'+delim+'\}'; 
       B; 
       '{\BS}end\{array\} \BS]' ];   /// \sleftarrow{{\normalfont concatenate matrix }}

mputl(text,'matrix.tex')   ///  \sleftarrow{{\normalfont a string matrix as text output in a file \verb+matrix.tex+}}

B=string(A);/// \sleftarrow{{\normalfont another way to build \verb+B+ } }
fmt='%d';  fmt = strcat(fmt(ones(1,na)),' &') + '{\BS}n';  /// \sleftarrow{{\normalfont building a format}}
B= msprintf(fmt,A)  /// \sleftarrow{{\normalfont builds a string vector using formatted output}}

B=string(A);/// \sleftarrow{{\normalfont again an other way to build \verb+B+}}
B=strcat(B,' & ','c');  /// \sleftarrow{{\normalfont concatenate \verb+B+ columns with an added separator}}

text= ['\BS[ A= {\BS}begin\{array\}\{'+delim+'\}';
        B + ' \BS\BS' ;   /// \sleftarrow{{\normalfont \verb+B+ is a column vector, we concatenate each row with ' \BS\BS' }}   
        '{\BS}end\{array\} \BS]' ]  /// \sleftarrow{{\normalfont matricial concatenation using  ``\verb-+-''}}
text=strsubst(text,'{\BS}','\');/// @@prerequisite
text=strsubst(text,'\{','{');   /// @@prerequisite
text=strsubst(text,'\}','}');   /// @@prerequisite
mputl(text,'matrix.tex')        /// @@prerequisite