└── README.md


/README.md:
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  1 | # Lua - Beginners Guide
  2 | 
  3 | ## Printing
  4 | ```lua
  5 | print("Hello World")
  6 | ```
  7 | 
  8 | ## Comments
  9 | ```lua
 10 | --this is a comment
 11 | print("hello") --this is another comment
 12 | -- the next line will not do anything because it is commented out
 13 | --print("world") 
 14 | ```
 15 | 
 16 | ## Variables
 17 | 
 18 | 
 19 | ```lua
 20 | -- Different types
 21 | local x = 10 --number
 22 | local name = "john doe" --string
 23 | local isAlive = false -- boolean
 24 | local a = nil --no value or invalid value
 25 | ```
 26 | 
 27 | **Numbers**
 28 | 
 29 | operators
 30 | - \+ addition
 31 | - \- minus
 32 | - \* multiply
 33 | - / divide
 34 | - ^ power
 35 | - % modulus
 36 | 
 37 | ```lua
 38 | -- examples
 39 | local a = 1
 40 | local b = 2
 41 | local c = a + b
 42 | print(c) -- 3
 43 | 
 44 | local d = b - a
 45 | print(d) -- 1
 46 | 
 47 | local x =  1 * 3 * 4 -- 12
 48 | print(x)
 49 | 
 50 | local y = (1+3) * 2 -- 8
 51 | print(y)
 52 | 
 53 | 
 54 | print(10/2) -- 5
 55 | print (2^2) -- 4
 56 | print(5%2) -- 1
 57 | 
 58 | print(-b) -- -2
 59 | ```
 60 | 
 61 | ```lua
 62 | -- increment
 63 | local level = 1
 64 | level = level + 1
 65 | print(level) -- 2
 66 | ```
 67 | 
 68 | **Strings**
 69 | ```lua
 70 | -- concatenate strings
 71 | local phrase = "My name is "
 72 | local name = "John Doe"
 73 | print(phase .. name) --My name is John Doe
 74 | 
 75 | -- strings and numbers
 76 | local age = 12
 77 | local name = "Billy"
 78 | print(name .. " is " .. age .. " years old")
 79 | ````
 80 | 
 81 | **Boolean**
 82 | ```lua
 83 | local isAlive = true
 84 | print(isAlive) --true
 85 | isAlive = false
 86 | print(isAlive) --false
 87 | ```
 88 | 
 89 | ## Conditional Statements
 90 | ```lua
 91 | --number comparisions
 92 | local age = 10
 93 | if age < 18 then
 94 |   print("over 18") --this will not be executed
 95 | end
 96 | 
 97 | --elseif and else
 98 | age = 20
 99 | if age > 18 then
100 |   print("dog")
101 | elseif age == 18 then
102 |   print("cat")
103 | else
104 |   print("mouse")
105 | end
106 | ```
107 | 
108 | **Comparison Operators**
109 | - == equality
110 | - < less than
111 | - \> greater than
112 | - <= less than or equal to
113 | - \>= greater than or equal to
114 | - ~= inequality
115 | 
116 | ```lua
117 | --boolean comparision
118 | local isAlive = true
119 | if isAlive then
120 |     print("dog")
121 | end
122 | 
123 | --string comparisions
124 | local name = "billy"
125 | if name == "Billy" then --false
126 |   print("Billy")
127 | elseif name == "billy" then --true
128 |   print("billy")
129 | end
130 | 
131 | ```
132 | 
133 | **Combining Statements**
134 | ```lua
135 | local x = 10
136 | if x == 10 and x < 0 then --both are true
137 |   print("dog")
138 | elseif x == 100 or x < 0 then --1 or more are true
139 |   print("cat")
140 | end
141 | --result: cat
142 | ```
143 | 
144 | **Nested statements**
145 | 
146 | ```lua
147 | local x = 10
148 | local isAlive = true
149 | if x==10 then
150 |   if isAlive == true then
151 |     print("dog")
152 |   else
153 |     print("cat")
154 |   end
155 | end
156 | ```
157 | **Invert Value**
158 | 
159 | you can also invert a value with the **not** keyword
160 | ```lua
161 | local x = 10
162 | if not x == 10 then
163 |   print("here")
164 | end
165 | ```
166 | 
167 | ## Functions
168 | ```lua
169 | function printTax(price)
170 |   local tax = price * 0.21
171 |   print("tax:" .. tax)
172 | end
173 | 
174 | printTax(200)
175 | ```
176 | 
177 | ```lua
178 | --function that returns a value
179 | function calculateTax(price)
180 |   return price * 0.21
181 | end
182 | 
183 | local result = calculateTax(100)
184 | print(result)
185 | 
186 | --reusing the function but this time using variables
187 | local bread = 130
188 | local milk = 110
189 | 
190 | local breadTax = calculateTax(bread) --27.3
191 | local milkTax = calculateTax(milk) --23.1
192 | 
193 | print("Bread Tax = " .. breadTax) 
194 | print("Milk Tax = " .. milkTax) 
195 | ```
196 | 
197 | ```lua
198 | --multiple parameters
199 | function displayInfo(name, age, country)
200 |   print(name .. " is " .. age .. " years old and is from " .. country)
201 | end
202 | 
203 | displayInfo("Billy", 12, "Jupiter")
204 | ```
205 | 
206 | ## Scope
207 | Variables have different scopes. Once the end of the scope is reached the values in that scope are no longer accessable
208 | ```lua
209 | function foo()
210 |   local a = 10
211 | end
212 | 
213 | print(a) --nil
214 | ```
215 | 
216 | ```lua
217 | local isAlive = true
218 | if isAlive then
219 |   local a = 10
220 | end
221 | 
222 | print(a) --nil
223 | ```
224 | 
225 | **Global Variable**
226 | ```lua
227 | local _G.myValue = 69
228 | --doing this can sometimes be bad practice
229 | ```
230 | 
231 | ## Loops
232 | There is a few different ways you can do a loop in lua
233 | ```lua
234 | --while loop
235 | local i = 0
236 | local count = 0
237 | 
238 | while i <= 10 do
239 |   count = count + 1
240 | end
241 | 
242 | print("count is " .. count) --count is 7
243 | 
244 | 
245 | --for loop
246 | count = 0
247 | for i=1, 5 do
248 |   count = count + 1
249 | end
250 | print("count is " .. count)
251 | 
252 | ```
253 | 
254 | **Infinite Loops**
255 | ```lua
256 | --infinite loop will never end
257 | local i = 0
258 | while i >= 0 do
259 |  i = i + 1
260 |  print(i)
261 | end
262 | ```
263 | 
264 | **Nested Loops**
265 | ```lua
266 | local count = 0
267 | for a=1, 10 do
268 |   for b=1, 10 do
269 |     count = count + 1
270 |   end
271 | end
272 | print(count) -- 100
273 | ```
274 | 
275 | 
276 | ## Tables
277 | ```lua
278 | --basic table
279 | local colors = { "red", "green", "blue" }
280 | 
281 | print(colors[1]) --red
282 | print(colors[2]) --green
283 | print(colors[3]) --blue
284 | 
285 | --using a loop to iterate though your table
286 | for i=1, #colors do
287 |   print(colors[i])
288 | end
289 | ```
290 | 
291 | **Table Manipulation**
292 | ```lua
293 | --insert
294 | local colors = { "red", "green", "blue" }
295 | table.insert(colors, "orange")
296 | local index = #colors --4 (this is the last index in the table)
297 | print(colors[index]) --orange
298 | ```
299 | 
300 | ```lua
301 | --insert at index
302 | local colors = { "red", "green", "blue" }
303 | table.insert(colors, 2, "pink")
304 | for i=1, #colors do
305 |   print(colors[i])
306 | end
307 | --red, pink, green, blue
308 | ```
309 | 
310 | ```lua
311 | --remove 
312 | local colors = { "red", "green", "blue" }
313 | table.remove(colors, 1)
314 | for i=1, #colors do
315 |   print(colors[i])
316 | end
317 | -- "green", "blue"
318 | ```
319 | 
320 | 
321 | **2 Dimensional Table**
322 | ```lua
323 | --tables within tables
324 | local data = {
325 |   { "billy", 12 },
326 |   { "john", 20 },
327 |   { "andy", 65 }
328 | }
329 | 
330 | for a=1, #data do
331 |   print(data[a][1] .. " is " .. data[a][2] .. " years old")
332 | end
333 | ```
334 | 
335 | 
336 | **Key Tables**
337 | 
338 | 2 dimensional tables are not suited to data with different types, instead uses keys for tables
339 | ```lua
340 | local teams = {
341 |     ["teamA"] = 12,
342 |     ["teamB"] = 15
343 | }
344 | 
345 | print(teams["teamA"]) -- 12
346 | 
347 | for key,value in pairs(teams) do
348 |   print(key .. ":" .. value)
349 | end
350 | ```
351 | 
352 | ```lua
353 | --insert into key table
354 | teams["teamC"] = 1
355 | ```
356 | 
357 | ```lua
358 | --remove key from table
359 | teams["teamA"] = nil
360 | ```
361 | 
362 | 
363 | **Returning a Table from a Function**
364 | 
365 | This can be used to return multiple values from a functions
366 | ```lua
367 | function getTeamScores()
368 |   local scores = {
369 |     ["teamA"] = 12,
370 |     ["teamB"] = 15
371 |   }
372 |   return scores
373 | end
374 | 
375 | local scores = getTeamScores()
376 | local total = 0
377 | for key, val in pairs(scores) do
378 |   total += val
379 | end
380 | print("Total score of all teams:" .. total)
381 | ```
382 | 
383 | 
384 | ## Math
385 | The math class has a number of functions for dealing with numbers. You may not need them but here is some of the more useful one functions:
386 | 
387 | More: [Wiki](http://lua-users.org/wiki/MathLibraryTutorial)
388 | 
389 | * abs (absolute value)
390 |   ```lua
391 |   local x = -10
392 |   print(math.abs(x)) --result: 10
393 |   local a = 10
394 |   print(math.abs(a)) --result: 10
395 |   ```
396 | * ceil (round up decimal value)
397 |   ```lua
398 |   local x = 1.2
399 |   print(math.ceil(x)) --result: 2
400 |   ```
401 | * deg (Convert value from radians to degrees)
402 |   ```lua
403 |   print(math.deg(math.pi)) -- result: 180
404 |   ```
405 | * floor (round down decimal value)
406 |   ```lua
407 |   local x = 1.2
408 |   print(math.floor(x)) --result: 1
409 |   ```
410 | * pi (constant value of pi)
411 |   ```lua
412 |   print(math.pi) --3.1415926535898
413 |   3.1415926535898
414 |   ```
415 | * rad (Convert value from degrees to radians)
416 |   ```lua
417 |   print(math.rad(180)) --result: 3.1415926535898
418 |   ```
419 | * random (random number generation)
420 |   ```lua
421 |   --random value between 0 tand 1
422 |   print(math.random()) --result: 0.0012512588885159
423 | 
424 |   --random integer value from 1 to 100 (both inclusive)
425 |   print(math.random(100)) --result: 20
426 | 
427 |   --random integer value from 20 to 100 (both inclusive)
428 |   print(math.random(20, 100)) --result: 54
429 |   ```
430 | * sqrt (Square root of a number)
431 |   ```lua
432 |   print(math.sqrt(100)) --result: 10
433 |   ```
434 | 
435 | ## Modules
436 | 
437 | Include code other files
438 | ```lua
439 | require("otherfile")
440 | ```
441 | 


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