5.6.9.5 Relational Operators
Relational operators are simple data operators that perform comparisons between their operands.
-
relational-operator-expression = equality-operator-expression / inequality-operator-expression / less-than-operator-expression / greater-than-operator-expression / less-than-equal-operator-expression / greater-than-equal-operator-expression
Static semantics:
§ Relational operators are statically resolved as simple data operators.
§ A relational operator is invalid if the declared type of any operand is an array or UDT.
§ A relational operator has the following declared type, based on the declared type of its operands:
|
Left Operand Declared Type |
Right Operand Declared Type |
Operator Declared Type |
|---|---|---|
|
Any type except an array, UDT or Variant |
Any type except an array, UDT or Variant |
Boolean |
|
Any type except an array or UDT |
Variant |
Variant |
|
Variant |
Any type except an array or UDT |
Variant |
Runtime semantics:
§ Relational operators are first evaluated as simple data operators.
§ If the value type of any operand is an array or UDT, runtime error 13 (Type mismatch) is raised.
§ Before evaluating the relational operator, its non-Null operands undergo Let-coercion to the operator’s effective value type.
§ The effective value type is determined as follows, based on the value types of the operands:
|
Left Operand Value Type |
Right Operand Value Type |
Effective Value Type |
|---|---|---|
|
Byte |
Byte, String or Empty |
Byte |
|
Byte, String or Empty |
Byte |
Byte |
|
Boolean |
Boolean or String |
Boolean |
|
Boolean or String |
Boolean |
Boolean |
|
Integer |
Byte, Boolean, Integer, String or Empty |
Integer |
|
Byte, Boolean, Integer, String or Empty |
Integer |
Integer |
|
Boolean |
Byte or Empty |
Integer |
|
Byte or Empty |
Boolean |
Integer |
|
Empty |
Empty |
Integer |
|
Long |
Byte, Boolean, Integer, Long, String or Empty |
Long |
|
Byte, Boolean, Integer, Long, String or Empty |
Long |
Long |
|
LongLong |
Any integral numeric type, String or Empty |
LongLong |
|
Any integral numeric type, String or Empty |
LongLong |
LongLong |
|
Single |
Byte, Boolean, Integer, Single, Double, String or Empty |
Single |
|
Byte, Boolean, Integer, Single, Double, String or Empty |
Single |
Single |
|
Single |
Long |
Double |
|
Long |
Single |
Double |
|
Double |
Any integral numeric type, Double, String or Empty |
|
|
Any integral numeric type, Double, String or Empty |
Double |
|
|
String |
String or Empty |
String |
|
String or Empty |
String |
String |
|
Currency |
Any integral or floating-point numeric type, Currency, String or Empty |
Currency |
|
Any integral or floating-point numeric type, Currency, String or Empty |
Currency |
Currency |
|
Date |
Any integral or floating-point numeric type, Currency, String, Date or Empty |
Date |
|
Any integral or floating-point numeric type, Currency, String, Date or Empty |
Date |
Date |
|
Decimal |
Any numeric type, String, Date or Empty |
Decimal |
|
Any numeric type, String, Date or Empty |
Decimal |
Decimal |
|
Null |
Any numeric type, String, Date, Empty, or Null |
Null |
|
Any numeric type, String, Date, Empty, or Null |
Null |
Null |
|
Error |
Error |
Error |
|
Error |
Any type except Error |
Runtime error 13 (Type mismatch) is raised. |
|
Any type except Error |
Error |
Runtime error 13 (Type mismatch) is raised. |
§ Relational comparisons can test whether operands are considered equal or if one operand is considered less than or greater than the other operand. Such comparisons are governed by the following rules, based on the effective value type:
|
Effective Value Type |
Runtime Semantics |
|---|---|
|
Byte, Integer, Long, LongLong, Currency, Decimal |
The numeric values of the operands are compared. Operands MUST match exactly to be considered equal. |
|
Single or Double |
The floating-point values of the operands are compared according to the rules of IEEE 754 arithmetic. If either operand is the special value NaN, runtime error 6 (Overflow) is raised. |
|
Boolean |
The Boolean values are compared. True is considered less than False. |
|
String |
The String values are compared according to the Option Compare comparison mode (section 5.2.1.1) setting of the enclosing module as follows: § If the active Option Compare comparison mode is binary-compare-mode (section 5.2.1.1), each byte of the implementation-specific representation of the string data is compared, starting from the byte representing the first character of each string. At any point, if one point is not equal to the other byte, the result of comparing those bytes is the overall result of the comparison. If all bytes in one string are equal to their respective bytes in the other string, but the other string is longer, the longer string is considered greater. Otherwise, if the strings are identical, they are considered equal. § If the active Option Compare comparison mode is text-compare-mode (section 5.2.1.1), the text of the strings is compared in a case-insensitive manner according to the platform’s host-defined regional settings for text collation. |
|
Null |
The result is the value Null. |
|
Error |
If both Error values are standard error codes, their numeric values (between 0 are 65535) are compared. If either value is an implementation-defined error value, the result of the comparison is undefined. |
§ There is an exception to the rules in the preceding table when both operands have a declared type of Variant, with one operand originally having a value type of String, and the other operand originally having a numeric value type. In this case, the numeric operand is considered to be less than (and not equal to) the String operand, regardless of their values.