Language Guide

CHAPTER 4
Commands
78 Using Command Definitions
Syntax 4
Each command definition begins with a syntax description, which is a
template for using the command in a statement. Syntax descriptions use the
same typographic conventions used elsewhere in this guide: plain computer
font indicates a language element you must type exactly as shown; italic text
indicates a placeholder you must replace with an appropriate value; brackets
indicate the enclosed language element or elements are optional; three ellipsis
points indicate you can repeat the preceding element or elements one or more
times; and vertical bars separate elements from which you must choose a
single element.
For example, to use the Move command, you must replace directParameter with
a reference to the object to move and location with a reference to the location to
which to move it.
Parameters 4
Parameters are values that are included with a command. The “Parameters”
section of a command definition lists the parameters of a particular command
and the information you need to use them correctly.
Many commands include a direct parameter that specifies the object of the
action. If a command includes parameters other than the direct parameter, they
are identified by labels. Parameters that are identified by labels are called
labeled parameters. The direct parameter immediately follows the command;
labeled parameters can be listed in any order. The Move command defined
in Figure 4-1 has a direct parameter (referred to in the definition as
referenceToObject) that specifies the object to move and a labeled parameter
(whose label is to) that specifies where to move the object.
Each parameter value must belong to a particular class, which is listed in its
description in the command definition. For the Move command, the direct
parameter belongs to the class reference. Its value, a reference, is a phrase that
identifies the object to be moved. The to parameter also belongs to the class
reference. It specifies the location to which to move the object. References are
described in Chapter 5, “Objects and References.”
Parameters can be required or optional. Required parameters must be
included with the command; optional parameters need not be. Optional
parameters are enclosed in brackets in syntax descriptions. For optional