Difference between revisions of "Basic Lua: Operators"

From The Official Visionaire Studio: Adventure Game Engine Wiki
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== Conditional Operators ==
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== Conditional Operators ==  
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{| class="ts"
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{|
 
|-
 
|-
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| [[Basic_lua:_Operators#if|if]] || Query if something does or does not meet a certain condition.
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| if || else || elseif || end
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|-
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|}
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| [[Basic_lua:_Operators#else|else]] || Do something else if the query condition was not met.
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|-
 
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| [[Basic_lua:_Operators#elseif|elseif]] || Used to add additional if queries, if the initial query condition was not met.
 
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|-
 
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| [[Basic_lua:_Operators#end|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.
 
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|}  
 
  
 
=== if ===
 
=== if ===
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</syntaxhighlight>
 
</syntaxhighlight>
 
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 <span class="green">true</span> & we haven't told the program what to do if the variable doesn't return <span class="red">false</span>, so let's do that now by using an '''else''' operator...
 
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 <span class="green">true</span> & we haven't told the program what to do if the variable doesn't return <span class="red">false</span>, so let's do that now by using an '''else''' operator...
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== else ==
 
<syntaxhighlight lang="lua">
 
<syntaxhighlight lang="lua">
 
local var = true
 
local var = true
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Because the variable contains a boolean value of <span class="green">true</span>, 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.
 
Because the variable contains a boolean value of <span class="green">true</span>, 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.
  
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=== else ===
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=== elseif ===
 
{| class="ts"
 
{| class="ts"
 
|-
 
|-
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end
 
end
 
</syntaxhighlight> || width="180px" | [[File:Basic_lua_(if_queries)_(4).png|frameless|center|180px]]
 
</syntaxhighlight> || width="180px" | [[File:Basic_lua_(if_queries)_(4).png|frameless|center|180px]]
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|}
 
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=== elseif ===
 
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{| class="ts"
 
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|-
 
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! if condition is not met, then do elseif !!
 
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|-
 
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| <syntaxhighlight lang="lua">
 
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local a = false
 
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if a then
 
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  print("a = true")
 
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elseif a == false then
 
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  print("a = false")
 
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end
 
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</syntaxhighlight> || width="180px" | [[File:Basic_lua_(if_queries)_(5).png|frameless|center|180px]]
 
 
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Revision as of 22:00, 2 November 2018

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

< Index >

Conditional Operators

if else elseif end


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

if condition is not met, then do else 
local a = false

if a then
  print("a = true")
else
  print("a = false")
end
Basic lua (if queries) (4).png

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
Basic lua (if queries) (6).png

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 )
click to enlarge
< Index >

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