Constants work differently to variables in the sense that they can only be
declared once. As of version 1.6.4, constants are defined
using the define
keyword:
define a = "Hello world"
Constants are then accessed by using the name of the constant:
$x = a
Predefined constants
ZPE provides several built in constants that can be accessed using their names:
| Constant name | Purpose | Value | Version added |
|---|---|---|---|
PI
|
The value of π | 3.141592653589793 | 1.3.3 |
PLANCK
|
The value of Planck's constant | 6.62606957-34 | 1.3.3 |
LIGHT_SPEED
|
The value of the speed of light | 2.997924588 | 1.3.3 |
COULOMB_CONSTANT
|
The value of Coulomb's Constant | 8.9875517879 | 1.3.3 |
EULER_NUMBER
|
The value of Euler's number | 2.7182818285 | 1.3.3 |
GRAVITATIONAL_CONSTANT
|
The gravitational constant | 6.67408-11 | 1.7.5 |
ATOMIC_MASS
|
The atomic mass constant | 1.6627 | 1.7.5 |
GOLDEN_RATIO
|
The value of the Golden Ratio | 1.6180339887498948482 | 1.7.5 |
ZPE_VERSION_MAJOR
|
The major version number of the ZPE instance used to compile the script. | Varies | 1.3.6 |
ZPE_VERSION_MINOR
|
The minor version number of the ZPE instance used to compile the script. | 1.3.6 | |
ZPE_CLI_VERSION
|
The CLI version number of the ZPE instance used to compile the script. | 1.3.6 |
From version 1.7.2 the way constants work was completely rewritten and made them very different from variables in the way they work as they are compiled at compile time into their values. For example:
$x = ZPE_VERSION_MAJOR
If this program was compiled and distributed, the value of the ZPE_VERSION_MAJOR constant would not change to the user's version of ZPE since it was precompiled with that value.
Prior to ZPE version 1.7.2
Prior to ZPE 1.7.2, constants were accessed using the name of the constant
preceded by a # symbol:
$x = #a
Prior to version 1.6.4, the constant was assigned in the same way it is accessed:
#a = 51 $x = #a
