Variables in HaasScript can be defined as either global or local. The difference between these two is that the other is accessible globally and the other is not:
-- This is a global variable (accessible globally)
myVariable = 1
-- This is a local variable (accessible locally)
local myVariable = 1
This means, that any variables defined as global will be visible everywhere in the script's scope, whereas the variables defined as local are only visible inside the scope they were first defined in but also in their sub-scopes.
Scope
To give you an example what a scope is in HaasScript, here's a script with an if-statement and a function:
-- We are inside the script's scope.
-- Variables defined here, either global or local,
-- are visible in sub-scopes within this script.
if something then
-- We are now inside the scope of an if-statement.
-- Local variables defined here are not visible outside.
end
local someFunction = function()
-- We are now inside the scope of a function.
-- Local variables defined here are not visible outside.
end
Inside if-statements
if something then
-- a global variable
thisIsGlobal = 5
-- a local variable
local thisIsLocal = 5 * 2
end
Log(thisIsGlobal) -- Outputs 5
Log(thisIsLocal) -- ERROR: Unknown references: thisIsLocal
Inside functions
local myFunction = function(value)
-- a global variable
thisIsGlobal = value
-- a local variable
local thisIsLocal = value * 2
end
-- Call the function
myFunction(5)
Log(thisIsGlobal) -- Outputs 5
Log(thisIsLocal) -- ERROR: Unknown references: thisIsLocal
Conflicting variables
Example of bad practice:
text = "Awesome text!"
local changeText = function(value)
text = value
end
changeText("..not anymore!")
Log(text) -- Outputs '..not anymore!'
Example of good practice:
local text = "Awesome text!"
local changeText = function(value)
-- 'text' is visible within this sub-scope, even when defined as local
Log(text) -- Outputs 'Awesome text!'
-- Local 'text' variable for this sub-scope
local text = value
end
changeText("..not anymore?")
Log(text) -- Outputs 'Awesome text!'
Overwriting variables in a function:
local text = "Awesome text!"
local changeText = function(text)
-- The input parameter 'text' will be
-- hiding the locally defined 'text',
-- so this Log() prints what
-- ever the input is.
Log(text)
end
changeText("..not anymore?") -- Outputs '..not anymore?'
Log(text) -- Outputs 'Awesome text!'
If
if condition then
end
if condition == true then
end
if condition == false then
end
if not condition then
end
If & Else
if condition1 then
else
end
If & ElseIf
if condition1 then
elseif condition2 then
end
If (One-liner)
Syntax:
local value = condition and value_if_true or value_if_false
Example:
local condition = true
local text = condition and "Condition is true." or "Condition is false."
Log(text) -- Outputs: Condition is true.
Booleans!?
local condition1 = false
local condition2 = true
Log("condition1:")
Log(condition1 and false or true) -- Outputs: true
Log(condition1 and true or false) -- Outputs: false
Log("condition2:")
Log(condition2 and false or true) -- Outputs: true
Log(condition2 and true or false) -- Outputs: true
Nil values and assignments
local variable
Log( variable and 'variable is not nil' or 'variable is nil')
-- Output: variable is nil
local variable = nil
Log( variable and 'variable is not nil' or 'variable is nil')
-- Output: variable is nil
local variable = 0
Log( variable and 'variable is not nil' or 'variable is nil')
-- Output: variable is not nil
local variable = ''
Log( variable and 'variable is not nil' or 'variable is nil')
-- Output: variable is not nil
local variable = false
Log( variable and 'variable is true' or 'variable false')
-- Output: variable is false
local variable = true
Log( variable and 'variable is true' or 'variable false')
-- Output: variable is true
Loading without default values
-- Load defaults to 'nil'
local powerLevel = Load('pl')
if not powerLevel then -- or 'if powerLevel == nil then'
powerLevel = 9001
Log('Power level set.')
end
Save('pl', powerLevel)
For each
The for each iterator returns the value of each element in the collection.
closePrices = ClosePrices()
for value in closePrices do
Log(value)
end
The iterator can also be used with key,value, if the key is defined.
object = { keyA = 'valueA', keyB = 'valueB'}
for key,value in pairs(object) do
Log(key .. " = " .. value)
end
Indexing
Lua's index is based on 1. You can use 0 as index in Lua, but HaasScript will throw you an error for it.
This restriction is implemented to break any confusions.
prices = ClosePrices()
price = prices[1] -- First price value in 'prices'
Accessing object fields
object = { keyA = 'valueA', keyB = 'valueB'}
Log(object.keyA) -- Outputs 'valueA'
Log(object.keyB) -- Outputs 'valueB'
Log(object.keyC) -- Outputs 'nil' (doesn't exist)
-- You can create new fields in objects
-- by assigning a value into them.
object.keyC = 'valueC'
Log(object.keyC) -- Outputs 'valueC'
For loop
All the for loops are based on a default structure. The init and max/min value are always required and the increment is optional (default +1)
for init, max/min value, [increment] do
-- Do something
end
Forward loop
Using # with the array variable will return the array size. This way we can easily loop over each value.
closePrices = ClosePrices()
for i = 1, #closePrices do
Log(closePrices[i])
end
Backwards loop
For the backwards loop we swap start and end value and set the increment to -1.
closePrices = ClosePrices()
for i = #closePrices, 1, -1 do
Log(closePrices[i])
end
Comments
HaasScript supports single- and multi-line comments.
-- Single-line comment
if commentingIsCool == true then
--[[ Multi-line comment, that
can continue through
multiple lines and
stop suddenly]] but = "allows code to continue"
end
--[[
This also works.
--]]
--[===[
And this.
--]===]
--[=[
This doesn't
--]==]
Arrays
Arrays are ordered arrangements of objects, which may be a one-dimensional array containing a collection of rows or a multi-dimensional array containing multiple rows and columns.
In HaasScript, arrays are implemented using indexing tables with integers. The size of an array is not fixed and it can grow based on your requirements, subject to memory constraints.
HaasScript also offers an alternative way for creating and manipulating arrays.
One-dimensional array
A one-dimensional array can be represented using a simple table structure and can be initialized and read using a simple for loop. An example is shown below.
array = {"HaasScript", "Tutorial"}
for i = 0, 2 do
Log(array[i])
end
When we run the above code, we will get the following output.
nil
HaasScript
Tutorial
As you can see in the above code, when we are trying to access an element in an index that is not there in the array, it returns nil. In HaasScript, indexing is limited to start at index 1. It is possible to create objects at index 0 and below 0 as well. Array using negative indices is shown below where we initialize the array using a for loop.
array = {}
for i= -2, 2 do
array[i] = i * 2
end
for i = -2, 2 do
Log(array[i])
end
When we run the above code, we will get the following output.
-4
-2
0
2
4
Multi-Dimensional Array
Multi-dimensional arrays can be implemented in two ways.
Array of arrays
Single dimensional array by manipulating indices
An example for multidimensional array of 3. 3 is shown below using array of arrays.
-- Initializing the array
array = {}
for i=1,3 do
array[i] = {}
for j=1,3 do
array[i][j] = i*j
end
end
-- Accessing the array
for i=1,3 do
for j=1,3 do
Log(array[i][j])
end
end
When we run the above code, we will get the following output.
1
2
3
2
4
6
3
6
9
An example for multidimensional array is shown below using manipulating indices.
-- Initializing the array
array = {}
maxRows = 3
maxColumns = 3
for row=1,maxRows do
for col=1,maxColumns do
array[row*maxColumns +col] = row*col
end
end
-- Accessing the array
for row=1,maxRows do
for col=1,maxColumns do
Log(array[row*maxColumns +col])
end
end
When we run the above code, we will get the following output.
1
2
3
2
4
6
3
6
9
As you can see in the above example, data is stored based on indices. It is possible to place the elements in a sparse way and it is the way Lua implementation of a matrix works. Since it does not store nil values in Lua, it is possible to save lots of memory without any special technique in Lua as compared to special techniques used in other programming languages.
