Chapter 3 The Application Description Language
Boolean Constants
Boolean constants must be one of the keywords TRUE or FALSE.
Integer Constants
Integer constants are always decimal and can be signed, e.g., 255, -1, +100000. The named integer constants MAX_INTEGER and MIN_INTEGER represent the values of the largest positive integer and the smallest negative integer on the host system.
Real Constants
Real constants follow the standard C language form of an integer part, a decimal point, an e or E, and an optionally signed integer exponent. At least one of the integer and fraction parts must be present, as well as either the decimal point or the exponent. Examples: 3.1416, 1E+9,
-0.21e-3.
The named floating point constants MAX_REAL and MIN_REAL represent the values of the largest and smallest positive real numbers that can be represented on the host system.
The REAL_EPSILON constant represents the smallest positive real value such that
0.0 + REAL_EPSILON != 0.0
String Constants
A string constant that contains only letters (A-Z, a-z), digits (0-9), or the underscore character
( _ ) can be so designated by preceding it with the single quote character ( ' ). This feature simplifies the specification of messages (see Section 3.13, "Messages" page 30). You can always enclose a string constant within double quotes ( " ), and you can embed the standard C escaped character constants[3] in strings.
| "Hello, world\n" |
| 'GetWidth |
Type Constants
Type constants can be one of the keywords booleanType, integerType, realType, stringType, vtypeType, handleType, listType, timeType, or intervalType.
Handle Constants
The only permissible handle constant is expressed by the keyword NULL. It represents a value that cannot be a valid handle to any variable or object. Thus, NULL indicates that a handle variable does not point to any valid target.
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