Trace (Arraylist subroutine)

Trace Arraylist (Arraylist class)

The Trace subroutine displays the contents of an Arraylist in a readable form on the currently selected trace stream, useful for debugging, for example. The listed item values are displayed in ascending order by their position and, by default, are preceded by their item number, a colon (':') and a blank.

Trace is identical to Audit and Print, except their output is sent to the Model 204 audit trail (like the User Language Audit statement) and user's standard output (terminal) destinations respectively.

Syntax

al:Trace[( [itemFunction], [NumWidth= number], [Separator= string], - [Start= number], [MaxItems= number], [Label= string])]

Syntax terms

al	An Arraylist object.
method	The method that is to be applied to al items to produce the trace output. The method must take no parameters and produce an intrinsic (be that Float, String, Fixed or Unicode) value. It may be a system or user-written method, a class variable or property, a local method, or a method variable. The default value of method is ToString.
NumWidth	The number of bytes in the display of each item to use for the item number. This is an optional parameter; if you specify a value, the parameter name NumWidth is required. Item numbers are right-justified within the indicated number of bytes, and they are truncated on the left if the length of the item number exceeds the space allocated for it. The NumWidth must be a number between -1 and 10 inclusive. If you specify a value of 0, the item number is not displayed. If NumWidth is -1, the default, the method uses the minimum number of bytes required to show the item number. For example, one byte is required for item number 5, while five bytes are required for item number 98764.
Separator	A string, 15 characters or less, to be used to separate the item number from the item value. This is an optional argument whose default is a colon (':'). A blank always follows the Separator string. If you specify a value, the parameter name Separator is required.
Start	The item number of the initial item in the output display. This is an optional argument, and it defaults to 1. If you specify a value, the parameter name Start is required.
MaxItems	The maximum number of items to display. A zero or negative value means to display all the items. This is an optional argument, and it defaults to zero. If you specify a value, the parameter name MaxItems is required.
Label	A literal string that gets output before each line. This is useful for "tagging" lines to make them more identifiable. This is an optional argument whose default is a null string. If you specify a value, the parameter name Label is required.

Usage notes

• All errors in Trace result in request cancellation.
• Audit and Print are the same as Trace except they send their output to the Model 204 audit trail or currently selected trace destinations, respectively.

Examples

1. For examples of Trace method calls, see Printing a collection.

See also

Arraylist class FloatNamedArraylist class NamedArraylist class UnicodeNamedArraylist class	List of Arraylist methods List of FloatNamedArraylist methods List of NamedArraylist methods List of UnicodeNamedArraylist methods List of Collection methods	Arraylist methods syntax FloatNamedArraylist methods syntax NamedArraylist methods syntax UnicodeNamedArraylist methods syntax
Notation conventions for methods