help with arrays (concatenate, indexof, splice)

Solar2D General Questions/Discussion
#1

i’ve posted some snippets from my collision, and have some questions around concat, indexof and splice. I’ve marked these up in the code. thanks for any help

( note: I use _.push for my array push from here http://mirven.github.com/underscore.lua )

[lua]-- ***** is this correct?
function indexof(t,e) return t[e] end
function splice(t,i) table.remove(t,i) end
– *****
– collision began (snippet)

obj1 = event.object1
obj2 = event.object2

if (obj1.actor == obj2.actor && obj1.actor.group[1] != obj1.actor.group[1]) then

obj1.actor.contacts.push(obj2.actor);
obj2.actor.contacts.push(obj1.actor);
– ***** need help doing this concatenate *******
– ***** what is the correct syntax for LUA? ****

obj1.actor.group = obj1.actor.group.concat(obj2.actor.group)

– *****

obj1.shareGroup()

– collision end (snippet)
obj1 = event.object1
obj2 = event.object2

if(obj1.actor.group.indexOf(obj2.actor) ~= nil) then

– ***** need help with the right syntax for splice (table.remove) & indexof *****
– ***** removes obj2 from obj1 contacts array, and obj1 from obj2’s

splice(obj1.actor.contacts,indexof(obj1.actor.contacts,obj2.actor))
splice(obj2.actor.contacts,indexof(obj2.actor.contacts,obj1.actor))

– *****

oldGroup = obj1.actor.group

for i=1, # oldGroup, 1 do

oldGroup[1].resetGroup()

end

obj1.actor.redefineGroup()
obj2.actor.redefineGroup()
obj1.actor.shareGroup()
obj2.actor.shareGroup()[/lua] [import]uid: 6645 topic_id: 3415 reply_id: 303415[/import]

#2

that != should be ~=

taking me a while to move over from other languages!

also my condition should be

[lua]if (obj1.actor == obj2.actor and obj1.actor.group[1] ~= obj2.actor.group[1]) then[/lua]
[import]uid: 6645 topic_id: 3415 reply_id: 10258[/import]

#3

i found these separately

[lua]function concat(t1, t2) for k,v in ipairs(t2) do table.insert(t1, v) end return t1 end

function splice(t,i) table.remove(t,i) end

function indexof(t,obj)

for k,v in pairs(t) do
if(v==obj) then return k end
end

end[/lua]

testing them at http://www.lua.org/cgi-bin/demo all seems to work fine

[lua]obj1 = {id = “iz obj1”}
obj2 = {id = “iz obj2”}
obj3 = {id = “iz obj3”}
obj4 = {id = “iz obj4”}

print("obj1.id "…obj1.id)

group1 = {obj1,obj2}
group2 = {obj3,obj4}

print(“concat group1 and group2”)
concat(group1,group2)
print(“group1[3]=”…group1[3].id)

print(“splice(group1,1) – removes obj1”)
splice(group1,1)
print(“group1[1]=”…group1[1].id)

temp = indexof(group1, obj4)

if(temp ~= nil) then print(“indexof(group1,obj4)=”…temp)
else print(“is nil”)
end[/lua]
[import]uid: 6645 topic_id: 3415 reply_id: 10262[/import]

#4

A more traditional splice, where you can chop out sections and replace with more loot.

NOTE: Not fully hashed out, can only “replaceWith” one “thing” (can’t insert another array)

[lua]function splice(t,i,len, replaceWith)
if (len > 0) then
for r=0, len do
if(r < len) then
table.remove(t,i + r)
end
end
end
if(replaceWith) then
table.insert(t,i,replaceWith)
end
local count = 1
local tempT = {}
for i=1, #t do
if t[i] then
tempT[count] = t[i]
count = count + 1
end
end
t = tempT
end[/lua]

Usage:
[lua]myArray = {1,2,3,4,5,6,7}

splice(myArray, 3, 1, “bob”)
– sets myArray to:
– 1,2,bob,4,5,6,7

splice(myArray, 3, 3, “bob”)
– sets myArray to:
– 1,2,bob,6,7[/lua] [import]uid: 616 topic_id: 3415 reply_id: 23401[/import]