Tutorial > Programming with PV-WAVE > Constants
  

Constants
A constant data type is determined by its syntax. In PV-WAVE there are eight basic data types, each with its own form of constant:
*BYTE—8-bit unsigned integers.
*INT—16-bit signed integers.
*INT32—32-bit signed integers.
*LONG—64-bit signed integers on 64-bit platforms; 32-bit signed integers on all other platforms.
*FLOAT—32-bit single-precision floating-point.
*DOUBLE—64-bit double-precision floating-point.
*COMPLEX—Real-imaginary pair using single-precision floating-point.
*DCOMPLEX—Real-imaginary pair using double-precision floating-point.
*STRING—Zero or more eight-bit characters which are interpreted as text.
Integer Constants
Numeric constants of different types may be represented by a variety of forms. The syntax of integer constants is shown in the following table, where “n” represents one or more digits.
 
Table 3-3: Syntax of Integer Constants 
Radix
Type
Form
Examples
Decimal
BYTE
nB
12B, 34B
INT
n
12, 425
INT32
nI
12I, 94I
LONG
nL
12L, 94L
Hexadecimal
BYTE
'n'XB
'2E'XB
INT
'n'X
'0F'X
INT32
nI
12I, 94I
LONG
'n'XL
'FF'XL
Octal
BYTE
"nB
"12B
INT
"n
"12
'n'O
'377'O
INT32
nI
12I, 94I
LONG
"nL
"12L
'n'OL
'777777'OL
Values of integer constants can range from 0 to 255 for BYTEs, 0 to ± 32,767 for INTs, 0 to ± 232 for INT32s, and 0 to ± 232 (on 32-bit systems) or 0 to ± 264 (on 64-bit systems) for LONGs. Integers that are initialized with absolute values greater than 32,767 are automatically typed as longword. Any numeric constant may be preceded by a + or a – sign. To ensure cross-platform compatibility, place the + or a – sign outside of the apostrophe.
Floating-point and Double-precision Constants
Floating-point and double-precision constants may be expressed in conventional or scientific notation. Any numeric constant that includes the decimal point is a floating-point or double-precision constant.
The syntax of floating-point and double-precision constants is shown in Syntax of Floating-point and Double-precision Constants. The notation sx represents the sign and magnitude of the exponent, for example:  E-2.
Double-precision constants are entered in the same manner, replacing E with a D. For example, 1.0D0, 1D, 1.D, all represent a double precision one.
 
Table 3-4: Syntax of Floating-point and Double-precision Constants  
Form
Double Precision
Floating Point
n .
102.D
102.
. n
.102D
.102
n .n
10.2D
10.2
n Xsx
10D5
10E5
n .Xsx
10.D–3
10.E–3
.n Xsx
.1D+12
.1E+12
n .n Xsx
2.3D12
2.3E12
Complex Constants
Complex constants contain a real and an imaginary part, which can be of single or double-precision floating point numbers. The imaginary part may be omitted, in which case it is assumed to be zero.
The form of a complex constant is:
COMPLEX(real_part, imaginary_part)
or:
COMPLEX(real_part)
For example, COMPLEX(1, 2), is a complex constant with a real part of one, and an imaginary part of two. COMPLEX(1)is a complex constant with a real part of one and a zero imaginary component.
The ABS function returns the magnitude of a complex expression. To extract the real part of a complex expression, use the FLOAT function; to extract the imaginary part, use the IMAGINARY function. These functions are explained in the PV‑WAVE Reference.
String Constants
A string constant consists of zero or more characters enclosed by apostrophes ( ' ) or quotation marks ( " ). The value of the constant is simply the characters appearing between the leading delimiter ( ' or " ) and the next occurrence of the delimiter.
A double apostrophe ( ' ' ) or double quotation mark ( " " ) is considered to be the null string; a string containing no characters.
An apostrophe or quotation mark may be represented within a string that is delimited by the same character, by two apostrophes, or quotation marks. For example, 'Don''t' produces Don't; or you can write: "Don't" to produce the same result.
Examples of Correct String Constants illustrates valid string constants.
 
Table 3-5: Examples of Correct String Constants  
String Value
Correct
Hi there
'Hi there'
Hi there
"Hi there"
Null String
''
I’m happy
"I'm happy"
I’m happy
'I''m happy'
counter
'counter'
129
'129'

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