6.1.2.2 Constants Module

Note

This section describes the implementation of MS-VBAL §6.1.2.2 Constants Module.

The Constants module is represented in the SDK by the interface IStdConstantsModule.

RD-VBA implements the eleven constants of MS-VBAL §6.1.2.2. Each is declared on IStdConstantsModule as the value it is: a static readonly field of a value type, in the order of the specification's table. Nothing implements the interface, because a constant is substituted where it is used, never called.

Constant	Type	Value
vbBack	String	Chr$(8)
vbCr	String	Chr$(13)
vbCrLf	String	Chr$(13) + Chr$(10)
vbFormFeed	String	Chr$(12)
vbLf	String	Chr$(10)
vbNewLine	String	🎯 Chr$(13) + Chr$(10), whatever platform the environment host runs on.
vbNullChar	String	Chr$(0)
vbTab	String	Chr$(9)
vbVerticalTab	String	Chr$(11)
vbNullString	String	A String bound to a null pointer rather than to a zero-length string (VBStringValue.VBNullString).
vbObjectError	Long	-2147221504

MS-VBAL §6.1.2.2 leaves vbNewLine and vbNullString implementation-defined. vbNewLine is the line break of a VBA String, which is the same on every platform. vbNullString compares equal to "" and has no data, so its Len and LenB are 0; a copy of it is still vbNullString (RD-VBAL §5.5.1.2.4 Let-coercion to and from String). A Declared procedure's ByVal String or ByVal As Any parameter given vbNullString receives a null pointer, where "" is a pointer to a zero-length string.

Note

Not implemented. A ByRef String parameter of a Declared procedure given vbNullString, and a String field that holds it in a record passed to one, are given a zero-length string instead of a null one: the BSTR they point to is an empty one.

Symbols

StdLibSymbolReader reads each field as a Public Const member of the Constants module, of the field's VBA type, whose value is a literal of the field's value (RD-VBAL §6.0.1 Symbol Injection). Like any constant, it has no storage: a use of it folds the value.

Public, because a module Const with no access modifier is not visible outside its module, and a constant has to reach the project scope to resolve unqualified, as the module's procedures do. A constant resolves unqualified (vbCrLf), qualified by its module (Constants.vbTab), and qualified by its library (VBA.vbCrLf). A Public constant that a standard module of the workspace declares under the same name shadows the library's, from any module. A variable named Constants that another standard module declares is what the name means, not this module (RD-VBAL §2.3.1.3 Name Resolution). A referenced library's member of that name is not: Excel's library declares an Enum Constants, and with Excel referenced the name is still this module, because MS-VBAL §5.6.10 ranks a referenced project's procedural module before the members of a referenced project's modules. Constants.xlAll is then VBC09316 Method or data member not found, and Excel's constant is Excel.Constants.xlAll, or xlAll alone.

In the type binding context too, Constants is this module ahead of Excel's Enum Constants, and a procedural module is not a type (MS-VBAL §5.6.16.7): Dim c As Constants is VBC09311 User-defined type not defined, with Excel referenced or not, and Excel's Enum is Excel.Constants. A user-defined type that another module of the project declares under the name Constants is the type (RD-VBAL §2.3.1.3 Name Resolution).

Note

Not implemented. A standard module of the workspace named Constants shares this module's scope, which is addressed by the module's name. A variable or a procedure it declares under one of these constants' names (Public vbTab As String) collides with the constant as a duplicate declaration where it is named through the module (Constants.vbTab) or used inside the module itself. Used unqualified from another module, it is the module's own, and a Public Const of such a name collides with nothing. A module named like another module of the library (Strings) collides with that module's members the same way.

A field that is not static readonly, or whose type is not a VBA value type, is refused when the library is read. A C# const is a primitive, whose VBA type would be a guess: a C# long is a VBA LongLong.

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⏮️ RD-VBAL §6.1.2.1 ColorConstants Module | ⏭️ RD-VBAL §6.1.2.3 Conversion Module