Compilare: user.cpp: In function ‘void sortinfold()’: user.cpp:28:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=c[l][0];k<=c[l][1];++k,++h)a[h]=d[k]; ^ user.cpp:29:24: warning: statement has no effect [-Wunused-value] if(l!=t-1){a[h]==',';++h;} ^ user.cpp: In function ‘int main()’: user.cpp:53:17: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] b[j]=NULL; ^ user.cpp:56:19: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] b[j+1]=NULL; ^ user.cpp:62:17: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] b[j]=NULL; ^