Hello again. Thank you all for your replies. Some interesting points raised.
Firstly, we have not used the gold standard for years.
Secondly we do not have to use simple operators alone: the values one to ten can be used, since humans use a decimal system (because we have ten fingers.)
For example
9
8
7
6
5
4
3
2
1
0
are used, then a column added to the left, and the symbols are RE-USED.
hence
Digit-Place
9-10
8-9
7-8
6-7
5-6
4-5
3-4
2-3
1-2
0-1
Ten distinct digits (or values.)
What about if I WROTE the following:
1<A<10
1<B<10
1<C<10
1<D<10
1<E<10
A+B*C-D/E
A+B*C/D-E
A+B-C*D/E
A+B-C/D*E
A+B/C-D*E
A+B/C*D-E
A*B+C-D/E
A*B+C/D-E
A*B-C+D/E
A*B-C/D+E
A*B/C+D-E
A*B/C-D+E
A-B+C*D/E
A-B+C*D/E
A-B*C+D/E
A-B*C/D+E
A-B/C+D*E
A-B/C*D+E
A/B+C*D-E
A/B+C-D*E
A/B*C+D-E
A/B*C-D+E
A/B-C+D*E
A/B-C*D+E
...or put another way
+=1, *=2,-=3,/=4,
1*2*3*4
As I stated, one of these permutations must produce some kind of intelligent result, if at all possible.
However in the interest of thoroughness we must also include the equals sign, because it, too, is an operator. It may produce a WRONG answer, but it is an answer nonetheless. Again a question is raised: must a computer always be correct, or can a wrong answer enable learning...???