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Learning Lua as a programer

Learning Lua as a programer [ edit page ]

After reading this you should proceed with Exploring the Stormworks Lua API

Theory

In case you did not read Learning Lua as a beginner

Lua variables have dynamic types:

myVariable = true
myVariable = 0.1

Lua variables do not need to be declared, but can (it influences scope):

myVariableA = 1
local myVariableB = 2

all index do start at 1, not at 0 (same is valid for strings: the first character is at position 1)!

myTable = {"a", "b"} -- myTable[1] = "a"
#myTable -- length of myTable = 2

Scope

by default, everything is in the global scope
you can declare variables to be local

function test()
	local myVariable = "hello"
	- can access myVariable here
end
-- cannot access myVariable here (myVaribale = nil)

Practical Examples

In the Lua IDE you can use the function

print()

. It's not supported in Stormworks, but it helps to create and debugs scripts in the Lua IDE.

Basic Math

myVariable = 1 + 2
print(myVariable) -- will output "3" to console

Copy this code into the Lua IDE and run it. If you scroll down a little bit, you can see the console output, now showing "3".

String formatting / Cutting away digits of numbers

Let's say you want to show a battery % label, from 1.0-100.0%. But the actual battery level is 0.12345 which would result in 12.345%.

battery = 0.12345
batteryPercent = battery * 100 -- 12.345
oneDecimalPlace = string.format("%0.1f", batteryPercent) -- "12.3"
print(oneDecimalPlace .. "%") -- "12.3%"
-- if you want two decimal place, use string.format("%0.2f", batteryPercent)

Write to and read from tables

myTable = {} -- create empty table
-- fill table
for i=1,5 do
	myTable[i] = i*5
end
-- print table
for k,v in ipairs(myTable) do
	print("k=" .. k, "v=" .. v)
end
-- this will print:
-- k=1 v=5
-- k=2 v=10
-- k=3 v=15
-- k=4 v=20
-- k=5 v=25

Create your own functions

This function simply adds 1 to the argument numb and returns the result.

function increment(numb)
	return numb + 1
end
print( increment(1) ) -- 2
print( increment(3.5) ) -- 4.5

Advanced table functions

table.insert() helps us to insert a new entry to an existing table:

myTable = {"a"}
table.insert(myTable, "b") -- will add entry at the end of the table (called push)


-- print table
for k,v in ipairs(myTable) do
	print("k=" .. k, "v=" .. v)
end
-- k=1 v="a"
-- k=2 v="b"
table.insert(myTable, 2, "c") -- will add entry at position 2 of the table
-- print table
for k,v in ipairs(myTable) do
	print("k=" .. k, "v=" .. v)
end
-- k=1 v="a"
-- k=2 v="c"
-- k=3 v="b"

The opposite of table.insert() is table.remove(), it removes an existing entry of an existing table.

myTable = {"a","b","c","d"}
value = table.remove(myTable) -- will remove the last entry of the table and return it to us (called pop)
print(value) -- "d"
-- print table
for k,v in ipairs(myTable) do
	print("k=" .. k, "v=" .. v)
end
-- k=1 v="a"
-- k=2 v="b"
-- k=3 v="c"


value = table.remove(myTable, 2) -- will remove the 2nd entry of the table and return it to us, it will also shift all the entries behind that (3,4,5,6,...) once index to the left to close the gap
print(value) -- "b"
-- print table
for k,v in ipairs(myTable) do
	print("k=" .. k, "v=" .. v)
end
-- k=1 v="a"
-- k=2 v="c"