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Section 8: Instrument programming Series 2600B System SourceMeter® instrument Reference Manual

8-22 2600BS-901-01 Rev. F/August 2021

Operator precedence

Operator precedence in Lua follows the order below (from higher to lower priority):

• ^ (exponentiation)

• not, - (unary)

• *, /

• +, –

• .. (concatenation)

• <, >, <=, >=, ~=, ==

• and

• or

You can use parentheses to change the precedences in an expression. The concatenation ("..") and

exponentiation ("^") operators are right associative. All other binary operators are left associative. The

examples below show equivalent expressions.

Equivalent expressions

reading + offset < testValue/2+0.5

(reading + offset) < ((testValue/2)+0.5)

3+reading^2*4

3+((reading^2)*4)

Rdg < maxRdg and lastRdg <=

expectedRdg

(Rdg < maxRdg) and (lastRdg <= expectedRdg)

-reading^2

-(reading^2)

reading^testAdjustment^2

reading^(testAdjustment^2)

Conditional branching

Lua uses the if, else, elseif, then, and end keywords to do conditional branching.

Note that in Lua, nil and false are false and everything else is true. Zero (0) is true in Lua.

The syntax of a conditional block is as follows:

if expression then

block

elseif expression then

block

else

block

end

Where:

• expression is Lua code that evaluates to either true or false

• block consists of one or more Lua statements

Tektronix KEITHLEY 2600B Series User Manual

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