Difference between revisions of "Lua for TIC80"

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Examples from: [https://github.com/btco/panda/blob/master/source/panda.lua 8-bit panda]
 
Examples from: [https://github.com/btco/panda/blob/master/source/panda.lua 8-bit panda]
 +
 +
More useful examples:
 +
 +
<source lang="lua">
 +
{x=0, y=0}
 +
</source>
 +
 +
is equivalent to
 +
 +
<source lang="lua">
 +
{["x"]=0, ["y"]=0}
 +
</source>
  
 
== if ==
 
== if ==

Revision as of 21:54, 31 January 2021

Like most (imperative) programming languages lua is based on variables, if-then and loop structures, and functions.

Assignment

See: https://www.lua.org/pil/4.1.html

Remember, unlike what you learned in your algebra class, the single equals sign in an assignment isn't about expressing a long term equality relationship. It's a transactional active structure that does two key things:

  1. evaluate / calculate the right hand side (RHS), then...
  2. store the computed value to a named reference (either a simple variable, or reference inside a table).

Once it's done the code continue and the same variable can be re-assigned to a new value, as in the frequent used case of incrementing a variable.

a = "hello" .. "world"
x = x + 1
t.n = tostring(x)

tables

Tables are the main data structure in Lua.

See:

Tables can be used to store a list of values. The # operator returns the last index (usually, see note below).

squares={1,4,9,16,25,36,49,64,81}

function TIC()
 cls(0)
 for i=1,#squares do
  print(i,i*16,0)
  print(squares[i],i*16,10)
 end
end

Tic80-table.png

Lua tables can also be like python dictionaries (and javascript objects)...

PLANE={
 START_FUEL=2000,
 MAX_FUEL=4000,
 FUEL_INC=1000,
 FUEL_BAR_W=50
}

Tables can be *nested* (one inside the other)...

LVL={
 {
  name="1-1",bg=2,
  palor={},
  pkstart=8,pklen=3,
  mus=BGM.A,
 },
 {
  name="1-2",bg=0,
  palor={[8]=0x102428},
  pkstart=11,pklen=2,
  mus=BGM.B,
 }
}

Examples from: 8-bit panda

More useful examples:

{x=0, y=0}

is equivalent to

{["x"]=0, ["y"]=0}

if

See: https://www.lua.org/pil/4.3.1.html

if btn(0) then
 t=t+1
elseif btn(1) then
 t=t-1
end

j94Lj.png

for

Tic80-forloop.png

See: https://www.lua.org/pil/4.3.4.html

function TIC()
 cls(0)
 
 for i=1,100,2 do
  rect(0,0,i,i,i%16)
 end

end

function

break, return

https://www.lua.org/pil/4.4.html