Difference between revisions of "Basic Lua: Operators"

Latest revision as of 22:15, 2 November 2018

Lua operators are expressions used to perform calculations or to pass arguments between different value types.

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Index

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Conditional Operators

if	Query if something does or does not meet a certain condition.
else	Do something else if the query condition was not met.
elseif	Used to add additional if queries, if the initial query condition was not met.
end	This is used to close various queries or functions; there must be the same amount of end as if; except in instances where elseif has been used.

if

if statements are one of the most common staples of programming, because programs & games & just about everything we do in life consists of if queries; should I wear this tie today? Do I need to go grocery shopping after work? Should I buy this game, or that game? etc. etc.

Let's say that we have a variable called var & we want to check if the var contains a boolean value of true...

local var = true

if var == true then
  print("var = true")
end

Quick note: if a variable contains a boolean value of true or false, then there is no need to use definitive query based operators as the variable on it's own will return the boolean value.

Now we want to perform the same query, but we want to check if the variable is false instead...

local var = true

if var == false then
  print("var = false")
end

What do you think will happen when we run the code above? That's right, absolutely nothing will happen because var still contains the boolean value of true & we haven't told the program what to do if the variable doesn't return false, so let's do that now by using an else operator...

else

local var = true

if var == false then
  print("var = false")
else
  print("var = true")
end

Because the variable contains a boolean value of true, we skip the if var == false block of code & execute the line of code in the else section instead, which would print "var = true" to the log.

elseif

Alternatively we can use elseif conditional operators instead of else to query multiple different statements. Below we are querying if var is true or false.

local var = true

if var == false then
  print("var = false")
elseif var == true then
  print("var = true")
end

end

This is pretty self-explanatory. All if queries, loops & functions require you to close them off with an end statement, the difference between them being that for nested if queries, there must be the same amount of end as there are if operators; the only exception to this rule is when you use elseif because it's not classed as a new if query but a continuation of the same query.

Logical Operators

and	Allows you to check multiple conditions in a single if query.
or	Allows you to add an alternative if query into a single if query.
not	Checks if condition equals false or negative.

and

if condition a is true and condition b is false then
local a = true local b = false if a == true and b == false then print("a = true", "b = false") end

or

if condition is true or condition == true then
local a = true if a or a == true then print("a = true") end	click to enlarge

not

if condition is not true
local a = false if not a then print("a = false") end	click to enlarge

Comparison Operators

==	Equal to.
~=	Does not equal.
>=	Greater than or equal to.
>	Greater than.
<=	Less than or equal to.
<	Less than.

equal to

if a equals 1
local a = 1 if a == 1 then print("a = 1") end	click to enlarge

does not equal

if a does not equal 2
local a = 1 if a ~= 2 then print("a = " .. a) end	click to enlarge

greater than or equal to

if a is greater than or equal to 2
local a = 5 if a >= 2 then print("a = " .. a) end	click to enlarge

greater than

if a is greater than 2
local a = 3 if a > 2 then print("a = " .. a) end	click to enlarge

less than or equal to

if a less than or equal to 2
local a = 2 if a <= 2 then print("a = " .. a) end	click to enlarge

less than

if a less than 2
local a = 0 if a < 2 then print("a = " .. a) end	click to enlarge

Mathematical Operators

+	Add
-	Subtract or invert
*	Multiply
/	Divide
^	Power
%	Remainder

add

1 + 2 = 3
local a = 1 local b = 2 local result = a + b print( result )	click to enlarge

subtract

3 - 2 = 1
local a = 3 local b = 2 local result = a - b print( result )	click to enlarge

inverse

inv of 3 = -3
local a = 3 local result = -a print( "original value: " .. a, "inversed value: " .. result )	click to enlarge

multiply

2 x 2 = 4
local a = 2 local result = a * a print( result )	click to enlarge

divide

10 ÷ 5 = 2
local a = 10 local b = 5 local result = a / b print( result )	click to enlarge

power

base of 2, power of 8 (2ⁿ) = 256

local a, b = 2, 16
local result = a ^ b -- generate answer
 
-- break down power function into string result (ignore this code)
function power(i1, i2)
 local val = "" -- clear string
 --+--
 for i = 1, i2 do -- generate the longhand math formula
  if i < i2 then val = val..i1.."*" else val = val..i1 end
 end
 return "which is the equivalent of " .. val
end
 
print("power value of "..a.." & "..b.."  = " .. result, power(a,b))

click to enlarge

remainder

remainder of 25 ÷ 4 = 1

local a = 25
local b = 4
local result = a / 4
local remainder = a % b
local decimal = remainder / b

print("result: 25 ÷ 4 = "  .. result, "remainder: .25 x 4 = " .. remainder, "decimal: 1 ÷ 4 = " .. decimal )