Data Types, Literals and Variables

Composite Strings

PxPlus provides the ability to define strings as a collection of data elements. These strings are called composite strings. A composite string is basically a record defined by an IOLIST statement consisting of variables and associated formats used to create the string.

Assigning data to a composite string causes the elements defined in the IOList to be loaded with their associated values. Referencing a composite string returns all the variables in their respective formats as defined by the IOList; thus, it can be considered a logical record or structure.

Note:
Composite strings cannot be used as object properties.

Defining a Composite String

The DIM directive is used to define a composite string. Provide the name of the string variable, a colon, and then the associated IOList.

Example:

To define a composite string consisting of 4 variables:

0100 DIM X$:IOL=1000
1000 IOLIST A$,B$,X,Y

or

0100 X_IOL$=PGM(1000); DIM X$:X_IOL$
1000 IOLIST A$,B$,X,Y

or

0100 DIM X$:CPL("IOLIST A$,B$,X,Y")

Unlike normal IOLists, the variables referenced in a composite string will be prefixed with the name of the composite string. Therefore, the variables in the above example referenced by X$ are not A$, B$, X, and Y but rather X.A$, X.B $, X.X, and X.Y. This is comparable to the REC= option found in input/output directives. See Processing Data Files.

Referencing a Composite String

When a program references a composite string, it will receive a string comprised of the variables defined in the IOList.

Example 1:

Given the following composite definition and values:

0100 DIM X$:IOL=1000
1000 IOLIST A$,B$,X,Y
X.A$="CAT", X.B$="DOG", X.X=1,X.Y=2

Referencing X$ will yield:

CAT - SEP - DOG - SEP - 1 - SEP - 2 - SEP -

Since the IOList specified general formatting of the data, each field was placed in ASCII in the output with a standard field separator (-SEP-) between them.

Example 2:

Given the following:

0100 DIM CST$:IOL=1000
1000 IOLIST NAME$:[CHR(20)],ADR1$:[CHR(20)]

CST.NAME$="PVX Plus Canada" CST.ADR1$="45B West Wilmot"

Referencing CST$ will yield:

"PVX Plus Canada 45B West Wilmot "

Since the IOList specified formatting, the output consists of the name (NAME$) padded to 20 characters, followed by a 20-character address (ADR1$).

Assigning Data to a Composite String

When a program updates a composite string, the variables that make up the composite will be updated automatically.

Example 1:

Given the following composite definition and values:

0100 DIM X$:IOL=1000
1000 IOLIST A$,B$,X,Y

X$="PVX PLUS"+SEP+"PXPLUS"+SEP+"123"

Will result in:

X.A$="PVX PLUS"
X.B$="PXPLUS"
X.X = 123
X.Y = 0

Since the data assigned to the composite string X$ only contains 3 fields, the fourth field (X.Y) will be set to zero.