6.1.2.11 Strings

Note

This section describes the implementation of MS-VBAL §6.1.2.11 Strings.

The Strings module is represented in the SDK by the interface IStdStringsModule.

The Strings module is declared in full. MS-VBAL §6.1.2.11 has 43 subsections, and RD-VBA's Strings module declares 55 members.

Some MS-VBAL subsections declare more than one member:

• the B-suffixed byte variants (InStrB, LeftB, LenB, MidB, RightB) share a subsection with the member they vary;
• the $-suffixed String-returning twins (Chr$, ChrB$, ChrW$) share a subsection with the member they vary;
• the LTrim / RTrim / Trim group is one subsection, and so is its $-suffixed twin.

Note

Not implemented. Of the Strings members, only Len and LenB have a runtime implementation. Calling any other member raises the run-time error "Application-defined or object-defined error".

6.1.2.11.1 Public Functions

Note

This section describes the implementation of MS-VBAL §6.1.2.11.1 Public Functions.

§	Member	Declared members	Notes
6.1.2.11.1.1	Asc / AscW	Asc
6.1.2.11.1.2	AscB	AscB
6.1.2.11.1.3	AscW	AscW
6.1.2.11.1.4	Chr / Chr$	Chr, Chr$
6.1.2.11.1.5	ChrB / ChrB$	ChrB, ChrB$
6.1.2.11.1.6	ChrW / ChrW$	ChrW, ChrW$
6.1.2.11.1.7	Filter	Filter
6.1.2.11.1.8	Format	Format
6.1.2.11.1.9	Format$	Format$
6.1.2.11.1.10	FormatCurrency	FormatCurrency
6.1.2.11.1.11	FormatDateTime	FormatDateTime
6.1.2.11.1.12	FormatNumber	FormatNumber
6.1.2.11.1.13	FormatPercent	FormatPercent
6.1.2.11.1.14	InStr / InStrB	InStr, InStrB
6.1.2.11.1.15	InStrRev	InStrRev
6.1.2.11.1.16	Join	Join
6.1.2.11.1.17	LCase	LCase
6.1.2.11.1.18	LCase$	LCase$
6.1.2.11.1.19	Left / LeftB	Left, LeftB
6.1.2.11.1.20	Left$	Left$
6.1.2.11.1.21	LeftB$	LeftB$
6.1.2.11.1.22	Len / LenB	Len, LenB	See §6.1.2.11.1.22.
6.1.2.11.1.23	LTrim / RTrim / Trim	LTrim, RTrim, Trim
6.1.2.11.1.24	LTrim$ / RTrim$ / Trim$	LTrim$, RTrim$, Trim$
6.1.2.11.1.25	Mid / MidB	Mid, MidB
6.1.2.11.1.26	Mid$	Mid$
6.1.2.11.1.27	MidB$	MidB$
6.1.2.11.1.28	MonthName	MonthName
6.1.2.11.1.29	Replace	Replace
6.1.2.11.1.30	Right / RightB	Right, RightB
6.1.2.11.1.31	Right$	Right$
6.1.2.11.1.32	RightB$	RightB$
6.1.2.11.1.33	Space	Space
6.1.2.11.1.34	Space$	Space$
6.1.2.11.1.35	Split	Split
6.1.2.11.1.36	StrComp	StrComp
6.1.2.11.1.37	StrConv	StrConv
6.1.2.11.1.38	String	String
6.1.2.11.1.39	String$	String$
6.1.2.11.1.40	StrReverse	StrReverse
6.1.2.11.1.41	UCase	UCase
6.1.2.11.1.42	UCase$	UCase$
6.1.2.11.1.43	WeekdayName	WeekdayName

6.1.2.11.1.22 Len / LenB

Note

This section describes the implementation of MS-VBAL §6.1.2.11.1.22 Len / LenB.

Strings.Len and Strings.LenB are the RD-VBA implementation of MS-VBAL §6.1.2.11.1.22. Both have a runtime implementation.

MS-VBAL says the pair returns "the number of characters in a string or the number of bytes required to store a variable on the current platform". It says LenB "will return the same value as Len, except for strings or UDTs": one function with two exceptions (strings and UDTs), rather than two functions.

Len and LenB are therefore implemented as one measurement, with one option that selects between them.

Expression	Len	LenB
A String	Its number of characters.	Two bytes per character.
A fixed-length String	Its declared length.	Twice its declared length.
Null	Null	Null
Any other scalar	The bytes it occupies.	The same as Len: the bytes it occupies.
A UDT	"the size as it will be written to the file"	"the in-memory size, including any implementation-specific padding between elements"

UDT sizes

The UDT row is the one that needs the platform to know two different sizes for the same value. 🎯 A UDT has two sizes: Len reports its serialized size (its members concatenated, with no padding), and LenB reports its in-memory size, which is also what VBUserDefinedTypeValue.Size reports.

RD-VBAL §2.5.2.1.3 User-Defined Type (UDT) Values defines both UDT sizes and holds the padding rule. Strings.Len and Strings.LenB make both sizes of a UDT observable to a program.

A record whose members include a variable-length String is the case MS-VBAL warns cannot be predicted: "Len might not be able to determine the actual number of storage bytes required when used with variable-length strings in user-defined data types". For such a record, Len counts the characters the member currently holds and LenB counts the pointer, so the two move independently of each other.

Declared types at external dispatch

👉 An external call carries runtime values rather than typed ones, so the declared type of the value a member was called with is recovered at external dispatch (RD-VBAL §5.3.1.11 Procedure Invocation Argument Processing). The declared type survives external dispatch because each intrinsic stores its own exact managed type: a short for Integer and an int for Long, not one integer type for both (RD-VBAL §2.5.2.1.1 Numeric Values).

👉 This is what lets Len return "the number of bytes required to store a variable" for the variable it is given. Date and Double are indistinguishable at external dispatch. That costs Len nothing, because they have the same width; a parameter declared Date will need its declared type to recover its argument.

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⏮️ RD-VBAL §6.1.2.10 Math | ⏭️ RD-VBAL §6.1.2.12 SystemColorConstants