Compilare: user.cpp: In function ‘int main()’: user.cpp:107:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<m-line.length();++j) line += space; ^ user.cpp:108:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<line.length();++j) ^ user.cpp:121:9: warning: unused variable ‘retlin’ [-Wunused-variable] int retlin = n,retcol = m; ^ user.cpp:121:20: warning: unused variable ‘retcol’ [-Wunused-variable] int retlin = n,retcol = m; ^