CHAPTER 3
52
Syntax
The following sections describe each object type, as well as how to create and
refer to indirect objects.
3.2.1 Boolean Objects
PDF provides
boolean objects
identified by the keywords
true
and
false
. Boolean
objects can be used as the values of array elements and dictionary entries, and can
also occur in PostScript calculator functions as the results of boolean and
relational operators and as operands to the conditional operators
if
and
ifelse
(see
3.2.2 Numeric Objects
PDF provides two types of numeric objects: integer and real.
Integer objects
rep-
resent mathematical integers within a certain interval centered at 0.
Real objects
approximate mathematical real numbers, but with limited range and precision;
they are typically represented in fixed-point form rather than floating-point
form. The range and precision of numbers are limited by the internal
representations used in the computer on which the PDF consumer application is
running; Appendix C gives these limits for typical implementations.
An integer is written as one or more decimal digits optionally preceded by a sign:
123
43445
+17
−98
0
The value is interpreted as a signed decimal integer and is converted to an integer
object. If it exceeds the implementation limit for integers, it is converted to a real
object.
A real value is written as one or more decimal digits with an optional sign and a
leading, trailing, or embedded period (decimal point):
34.5
−3.62
+123.6
4.
−.002
0.0
The value is interpreted as a real number and is converted to a real object. If it
exceeds the implementation limit for real numbers, an error occurs.
Note:
PDF does not support the PostScript syntax for numbers with nondecimal
radices (such as
16#FFFE
) or in exponential format (such as
6.02E23
).