5.6.9.5 Relational Operators

Note

This section describes the implementation of MS-VBAL §5.6.9.5 Relational Operators.

Runtime Semantics

Relational operators are simple data operators: they validate their operands through OperatorRuntimeSemantics.LetCoerceNonNullOperand (RD-VBAL §5.6.9.2 Simple Data Operators).

Relational operators compare in the effective type, and yield a VBBooleanValue.

Effective type	Compared in
Integral	The effective type's own representation: for example `Long` as a 32-bit `int`, and `LongLong` as a 64-bit `long`.
`Boolean`	A 64-bit integer (`long`).
Fixed-point (`Currency`, `Decimal`)	`decimal`

Condition	Run-time error
An operand is `NaN`.	6 — Overflow

Run-time error 6 is VBRuntimeErrorId.Overflow.

👉 The range checks of a For loop use the relational operators RDCore.Runtime.Semantics.Operators.Relational.BinaryGtRelationalOperatorRuntimeSemantics and BinaryLtRelationalOperatorRuntimeSemantics, not a raw numeric comparison (RD-VBAL §5.4.2.3 For Statement).

Variant String/Numeric comparison

RD-VBA implements the Variant String/Numeric comparison exception of MS-VBAL §5.6.9.5 as run-time behaviour.

The exception applies when both relational operands are Variant, one originally holding a String value and the other a numeric value:

The numeric operand is always considered less than the String operand, regardless of their actual values.
RD-VBA never attempts to coerce the String operand to a number. Depending on its content, that coercion would fail, or succeed incorrectly.

BinaryRelationalOperatorRuntimeSemantics handles the exception as a short-circuit:

It detects the Variant String/Numeric case before normal effective-type determination and coercion run.
It reduces the case to a synthetic Integer rank for each operand (table below).
The relational operator's ordinary Integer evaluation branch compares the synthetic ranks.

Operand	Synthetic `Integer` rank
The numeric-holding `Variant`	`0`
The `String`-holding `Variant`	`1`

The short-circuit runs before normal coercion because normal coercion would otherwise try, and fail, to coerce the String to a number. Because the case is reduced to synthetic ranks, the Variant String/Numeric case needs no separate evaluation path.