Returning - What does it mean?

[Drakehawke]

Usually at the end of a function, there's a 'return' with something after it, I have a vague idea what it means but a clear explanation would be nice.

[Lily]

Example:
[lua]function booz()
return "foo"
end
print(booz())
[/lua]

Output: foo
Basicly booz outputs foo, which is sent to the print that prints it.

[MakeR]

Returning basically means to send values back to where the function was called from.

[lua]function foo(a, b) -- foo take two arguments
return a+b -- and returns the addition of them
end

local r = foo(1, 4) -- r will now hold 1+4
print(r) -- Output: 5 as expected.[/lua]

[editline]04:32PM[/editline]

You can return any Lua value, such as tables, numbers, strings. You can also return multiple values, like this:

[lua]function bar(a, b, c, d)
return a+b, c+d
end

local r, s = bar(1, 4, 5, 5)
print(r, s) -- Output: 5 10[/lua]

[Drakehawke]

Ahhh, I get it now, thank you :)

[Lexic]

Note, 'return' on it's own means "Stop the function here, I want to get off.", and is equivalent to 'return nil'

[Drakehawke]

[QUOTE=Lexic;22063842]Note, 'return' on it's own means "Stop the function here, I want to get off.", and is equivalent to 'return nil'[/QUOTE]

Don't quite get that..

[Lily]

Example:
[lua]function foo()
return
print("bar")
end
foo()
[/lua]

Will not do anything becuse the return stops the function and jumps back to the line where it was called

[userman122]

Thanks. I dindt knew that.

[Drakehawke]

Ohhhhhhhhhh, I see, so what's the difference between:

[LUA]
function foo()
print("bar")
return
end
foo()
[/LUA]
and
[LUA]
function foo()
print("bar")
end
foo()
[/LUA]

[Lexic]

Ignoring the extra 'end' on the second one, nothing, other than you are explicitly saying 'return'. If you don't do that, Lua puts a 'return' at the end for you.

[userman122]

It doesent use the keyword return..??

[Lily]

theres no diff between them, as the return is at the end. it stops at the return

[userman122]

Ok. So the return doesent do anything in this example?

[Lexic]

Return on it's own can also be used to slim down if pyramids.
For example:
[lua]function plugh()
if (ply.foo) then
print("You cannot foo!");
else
bar()
if (ply.baz) then
print("You cannot baz!")
else
qux()
if (ply.quux) then
print("You cannot quux!")
else
garply()
end
end
end
end[/lua]
Can be compressed down to
[lua]function plugh()
if (ply.foo) then
print("You cannot foo!");
return
end
bar()
if (ply.baz) then
print("You cannot baz!")
return;
end
qux()
if (ply.quux) then
print("You cannot quux!")
return;
end
garply()
end[/lua]
Which I personally think looks much neater.

[Drakehawke]

Is return "" the same as return?

[Lily]

Not really
[lua]function A()
return ""
end
print(type(A()))
-- Output: String

function B()
return
end
print(type(B()))
-- Output: nil
[/lua]

[|FlapJack|]

[QUOTE=Drakehawke;22143693]Is return "" the same as return?[/QUOTE]

returning "" returns an empty string, which is not nil.

[Crazy Quebec]

[QUOTE=Tobba;22067161]Example:
[lua]function foo()
return
print("bar")
end
foo()
[/lua]

Will not do anything becuse the return stops the function and jumps back to the line where it was called[/QUOTE]

A bit late but note that this example is invalid. You can't have anything after a return statement in any given "block" of code.

[editline]11:42AM[/editline]

[url]http://www.lua.org/pil/4.4.html[/url]

[MakeR]

[QUOTE=Crazy Quebec;22145375]A bit late but note that this example is invalid. You can't have anything after a return statement in any given "block" of code.

[editline]11:42AM[/editline]

[url]http://www.lua.org/pil/4.4.html[/url][/QUOTE]

[QUOTE=Tobba;22067161]Example:
[lua]function foo()
return
print("bar")
end
foo()
[/lua]

Will not do anything becuse the return stops the function and jumps back to the line where it was called[/QUOTE]

Tobba's function is actually valid and will actually print 'bar' (which defeats the purpose of his example). however, this isn't:

[lua]function foo()
return;
print("bar")
end[/lua]

In Tobba's example the function returns the return value from print("bar"), so the print actually gets called. In my example the semi-colon prevents this.

[editline]04:48PM[/editline]

This happens because Lua doesn't use whitespace to end statements.

[Crazy Quebec]

[QUOTE=MakeR;22145501]Tobba's function is actually valid and will actually print 'bar' (which defeats the purpose of his example). however, this isn't:

[lua]function foo()
return;
print("bar")
end[/lua]

In Tobba's example the function returns the return value from print("bar"), so the print actually gets called. In my example the semi-colon prevents this.

[editline]04:48PM[/editline]

This happens because Lua doesn't use whitespace to end statements.[/QUOTE]

Ah you are right.

[Lily]

I just suck at adding spaces instead of tabs

[Crazy Quebec]

[QUOTE=iRzilla;22145841]You serious?

I thought semi colons were obsolete...[/QUOTE]

They were never obsolete for they never were valid to use in lua. But Garry's Mod lua has them and they can be used to end a line, which is of course completely pointless to do in lua save for that very case Maker posted.

[MakeR]

[QUOTE=Crazy Quebec;22145921]They were never obsolete for they never were valid to use in lua. But Garry's Mod lua has them and they can be used to end a line, which is of course completely pointless to do in lua save for that very case Maker posted.[/QUOTE]

They are valid in pure Lua.

[editline]05:11PM[/editline]

[QUOTE=Tobba;22145877]I just suck at adding spaces instead of tabs[/QUOTE]

Doesn't matter, it would happen with any white space (including tab).

[editline]05:14PM[/editline]

There is literally almost no case where you would do what Tobba posted anyway, normally a return would either be followed by the function end, or an else/elseif statement.

[Drakehawke]

[QUOTE=|FlapJack|;22144039]returning "" returns an empty string, which is not nil.[/QUOTE]

In what case would you want to return an empty string instead of just nil?

[MakeR]

In [b][url=wiki.garrysmod.com/?title=Gamemode.PlayerSay]Gamemode.PlayerSay [img]http://wiki.garrysmod.com/favicon.ico[/img][/url][/b] I guess.

[Crazy Quebec]

[QUOTE=MakeR;22145936]They are valid in pure Lua.[/QUOTE]

Aw this ain't my day. I somehow always thought it was Garry who added them with all of his C syntax additions..

[Drakehawke]

[QUOTE=MakeR;22146332]In [b][url=wiki.garrysmod.com/?title=Gamemode.PlayerSay]Gamemode.PlayerSay [img]http://wiki.garrysmod.com/favicon.ico[/img][/url][/b] I guess.[/QUOTE]

confused

[Jam]

[QUOTE=Drakehawke;22148773]-confused face-[/QUOTE]

For example,

[lua]function DonatorChat( ply, text, toall )
if !ply:IsSuperAdmin() then return end
if (string.sub(text, 1, 8) == "!donator") then
ply:ConCommand("donator "..string.Right(text, string.len(text)-8))
return ""
end
end
hook.Add( "PlayerSay", "DonatorChat", DonatorChat )[/lua]

Thats what I use in my donation system. It stops !donator from showing in the chat.

[HeavyMtl123]

[QUOTE=Drakehawke;22148773]-confused face-[/QUOTE]

Well hopefully all the poeple replying to this will have made it easier to understand, Lua is a hard nut to crack, so to speak, but it will just come to you if you spend some time pushing your boundaries.

[Drakehawke]

[QUOTE=Jamie932;22149108]For example,

[lua]function DonatorChat( ply, text, toall )
if !ply:IsSuperAdmin() then return end
if (string.sub(text, 1, 8) == "!donator") then
ply:ConCommand("donator "..string.Right(text, string.len(text)-8))
return ""
end
end
hook.Add( "PlayerSay", "DonatorChat", DonatorChat )[/lua]

Thats what I use in my donation system. It stops !donator from showing in the chat.[/QUOTE]

I understand all that apart from
[lua]
ply:ConCommand("donator "..string.Right(text, string.len(text)-8))
[/lua]