Hey, hello! I'm a beginner in programming. I followed the tutorial "Game Development using PICO-8 by Dylan Bennett" to learn to use Pico-8. follow the page 28 of the tutorial. I wrote a game which just like "Flappy Bird", and then I ran into some questions about "tables".
The questions are as follows:
I don't understand what the means about"cave={{["top"]=5,["btm"]=119}}".
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The context of this code is as follows（In line 2）：
function make_cave()
cave={{["top"]=5,["btm"]=119}}
top=45
btm=85
end
function update_cave()
if (#cave>player.speed) then
for i=1,player.speed do
del (cave,cave[1])
end
end
while (#cave<128) do
local col={}
local up=flr(rnd(7)-3)
local dwn=flr(rnd(7)-3)
col.top=mid(3,
cave[#cave].top+up,top)
col.btm=mid(btm,
cave[#cave].btm+dwn,124)
add(cave,col)
end
end
function draw_cave()
top_color=5
btm_color=5
for i=1,#cave do
line(i-1,0,i-1,cave[i].top,
top_color)
line(i-1,127,i-1,cave[i].btm,
btm_color)
end
end |
Basically when you have double curly braces like that, it means "a table of tables". You're making a table where the items in the table are made up of... more tables. So this code...
things = {
{5, 6},
{9, 4},
{3, 4}
} |
...would mean you have a table called things that has 3 items in it. Each item is a table. Those tables each have their own 2 items (the numbers). I hope that makes sense.
some info in in official doc: https://www.lexaloffle.com/dl/docs/pico-8_manual.html#Tables
more in books like programming in lua (read the version for lua 5.2, which pico8 is based on)
-- tables are data structures that associate keys and values
t1 = {}
t1["a"] = "keys can be strings"
t1[true] = "keys can be other types!"
t1.b = "string keys have this shortcut notation"
t2 = {
["a"]="create table and contents in one go",
[true]="just need these brackets before = sign",
b="unless you use this shortcut for strings! no bracket or quotes but same result",
}
-- tables can also be used to store an ordered list of things
t3 = {}
add(t3, 10)
add(t3, 20)
add(t3, 30)
del(t3, 20)
# the functions automatically give keys 1,2,3 etc for the values
# t3[1] == 10 and t3[2] == 30 !
t4 = { 10, 20, 30, 20, 12 } -- create table and contents in one go
-- it is common to mix them!
all_goblins = {}
goblin1 = { x=10, y=10, health=21 }
add(all_goblins, goblin1)
goblin2 = { x=40, y=10, health=42 }
add(add_goblins, goblin2)
-- this one is also a table-as-sequence of tables-as-objects (with key-values)
fairies = {{sp=10}, {sp=11}, {sp=12}} |
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