Model 2461 Interactive SourceMeter® Instrument Reference Manual
Section 7: Introduction to TSP operation
2461-901-01 A/November 2015
7-13
Values and variable types
In Lua, you can use variables to store values in the run-time environment for later use.
Lua is a dynamically-typed language; the type of the variable is determined by the value that is
assigned to the variable.
Variables in Lua are assumed to be global unless they are explicitly declared to be local. A global
variable is accessible by all commands. Global variables do not exist until they have been assigned a
value.
Variable types
Variables can be one of the following types.
Variable types and values
Variable type returned
Value
Notes
"nil"
not declared
The type of the value
nil
, whose
main property is to be different from
any other value; usually it represents
the absence of a useful value.
"boolean"
true or false
Boolean is the type of the values
false
and
true
. In Lua, both
nil
and
false
make a condition
false
; any other value makes it
true
.
"number"
number
All numbers are real numbers; there
is no distinction between integers
and floating-point numbers.
Hexadecimal and binary values are
also handled as the number type in
TSP.
"string"
sequence of words or
characters
"function"
a block of code
Functions perform a task or compute
and return values.
"table"
an array
New tables are created with { }
braces. For example,
{1, 2, 3.00e0}.
"userdata"
variables
Allows arbitrary program data to be
stored in Lua variables.
"thread"
line of execution
To determine the type of a variable, you can call the
type()
function, as shown in the examples
below.
The output you get from these examples may vary depending on the data format that is set.
Example: Nil
x = nil
print(x, type(x))
nil nil