Basic lua: Operators

From The Official Visionaire Studio: Adventure Game Engine Wiki
Revision as of 14:42, 21 August 2014 by AFRLme (talk)

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

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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.
Example 1: if condition is true (method 1)
local a = true

if a then
 print("a = true")
end
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Example 2: if condition is true (method 2)
local a = true

if a == true then
 print("a = true")
end
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Example 3: if condition is false
local a = false

if a == false then
 print("a = false")
end
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Example 4: if condition is not met, then do else
local a = false

if a then
 print("a = true")
else
 print("a = false")
end
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Example 5: if condition is not met, then do elseif
local a = false

if a then
 print("a = true")
elseif not a then
 print("a = false")
end
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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.
Example 1: 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
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Example 2: if condition is true or condition == true then
local a = true

if a or a == true then
 print("a = true")
end
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Example 3: if condition is not true
local a = false

if not a then
 print("a = false")
end
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Comparison Operators

== Equal to.
~= Does not equal.
>= Greater than or equal to.
> Greater than.
<= Less than or equal to.
< Less than.
Example 1: if a equals 1
local a = 1

if a == 1 then
 print("a = 1")
end
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Example 2: if a does not equal 2
local a = 1

if a ~= 2 then
 print("a = " .. a)
end
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Example 3: if a is greater than or equal to 2
local a = 5

if a >= 2 then
 print("a = " .. a)
end
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Example 4: if a is greater than 2
local a = 3

if a > 2 then
 print("a = " .. a)
end
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Example 5: if a less than or equal to 2
local a = 2

if a <=  2 then
 print("a = " .. a)
end
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Example 6: if a less than 2
local a = 0

if a <  2 then
 print("a = " .. a)
end
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Mathematical Operators

+ Add
- Subtract or invert
* Multiply
/ Divide
^ Power
% Remainder
Example 1: 1 +2 = 3
local a = 1
local b = 2
local result = a + b

print( result )
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Example 2: 3 - 2 = 1
local a = 3
local b = 2
local result = a - b

print( result )
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Example 3: inversed values
local a = 3
local result = -a

print( "original value: " .. a, "inversed value: " .. result )
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Example 4: 2 x 2 = 4
local a = 2
local result = a * a

print( result )
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Example 5: 10 ÷ 5 = 2
local a = 10
local b = 5
local result = a / b

print( result )
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Example 6: base of 2, power of 8 (2ⁿ) = 256
local a = 2
local b = 8
local result = 2 ^ 8

-- break down power function into string result (ignore this code)
function power(i1, i2)
 local val = ""
 --+--
 for i = 1, i2 do
  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 2 & 8 = " .. result, power(a,b))
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Example 7: 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 )
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