Compilare: user.cpp: In function ‘int main()’: user.cpp:42:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(a);i++) ^ user.cpp:44:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=i+1;j<strlen(a);j++) ^ user.cpp:46:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(a);i++) ^ user.cpp: In function ‘int val(char)’: user.cpp:38:1: warning: control reaches end of non-void function [-Wreturn-type] } ^