Keithley 2657A

Model 2657A High Power System SourceMeter® Instrument Reference Manual Section 6: Instrument programming
2657A-901-01 Rev. B/December 2012 6-21
While loops
To use conditional expressions to determine whether to execute or end a loop, you use while loops.
These loops are similar to Conditional branching
(on page 6-19) statements.
while expression do
block
end
Where:
• expression is Lua code that evaluates to either true or false
• block consists of one or more Lua statements
Example: While
list = {
"One", "Two", "Three", "Four", "Five", "Six"}
print("Count list elements on numeric index:")
element = 1
while list[element] do
print(element, list[element])
element = element + 1
end
This loop exits when list[element]
= nil.
Output:
Count list elements on
numeric index:
1.00000e+00 One
2.00000e+00 Two
3.00000e+00 Three
4.00000e+00 Four
5.00000e+00 Five
6.00000e+00 Six
Repeat until loops
To repeat a command, you use the repeat ... until statement. The body of a repeat statement
always executes at least once. It stops repeating when the conditions of the until clause are met.
repeat
block
until expression
Where:
• block consists of one or more Lua statements
• expression is Lua code that evaluates to either true or false
Example: Repeat until
list = {
"One", "Two", "Three", "Four", "Five", "Six"}
print("Count elements in list using repeat:")
element = 1
repeat
print(element, list[element])
element = element + 1
until not list[element]
Output:
Count elements in list
using repeat:
1.00000e+00 One
2.00000e+00 Two
3.00000e+00 Three
4.00000e+00 Four
5.00000e+00 Five
6.00000e+00 Six