Comparison of index-names and index data items
Comparisons involving index-names, index data items, or both conform to rules.
The rules for comparisons are:
- The comparison of two index-names is actually the comparison of the corresponding occurrence numbers.
- In the comparison of an index-name with a data item (other than an index data item), or in the comparison of an index-name with a literal, the occurrence number that corresponds to the value of the index-name is compared with the data item or literal.
- In the comparison of an index-name with an arithmetic expression,
the occurrence number that corresponds to the value of the index-name
is compared with the arithmetic expression.
Because an integer function can be used wherever an arithmetic expression can be used, you can compare an index-name to an integer or numeric function.
- In the comparison of an index data item with an index-name or another index data item, the actual values are compared without conversion. Results of any other comparison involving an index data item are undefined.
Valid comparisons for index-names and index data items are shown in the following table.
| Operands compared | Index-name | Index data item | Data-name (numeric integer only) | Literal (numeric integer only) | Arithmetic Expression |
|---|---|---|---|---|---|
| Index-name | Compare occurrence number | Compare without conversion | Compare occurrence number with content of referenced data item | Compare occurrence number with literal | Compare occurrence number with arithmetic expression |
| Index data item | Compare without conversion | Compare without conversion | Invalid | Invalid | Invalid |