The permissible combinations of variables, numeric literals, arithmetic operator and parentheses are given in Table 1.
| First Symbol | Second Symbol | ||||
|---|---|---|---|---|---|
| Variable | * / ** + - B-AND B-OR B-XOR B-EXOR | Unary + - B-NOT | ( | ) | |
| Variable | - | P | - | - | P |
| * / ** + - B-AND B-OR B-XOR B-EXOR | P | - | P | P | - |
| Unary + - B-NOT | P | - | - | P | - |
| ( | P | - | P | P | - |
| ) | - | P | - | - | P |
| P | indicates a permissible pair of symbols |
| - | indicates an invalid pair |
| Variable | indicates an identifier or literal |