Require any string?

[T-Bone]

I've had some issues with the require function. My game creates .lua files for game maps, and I want to run them using the require function. The .lua files are named map1.lua, map2.lua and so on. If you specify which one you want, like this

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require 'map2.lua'

it works great. However, if I want to run map number 'mapNbr', it doesn't work.

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require 'map'..mapNbr..'.lua'

does not work. I get an error

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unexpected symbol near '..'

. Any workaround? I really don't want to do like

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if lvlNbr==1 then require map1.lua 
elseif lvlNbr==2 then require map2.lua

Any ideas?

[bartbes]

Because the parenthesis-less invocation only works with literals, not with variables. Require is a function like any other.
I will also note that the suffix ".lua" is wrong and deprecated, and is removed for 0.8.0.
So you'll end up with:

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require("map" .. mapNbr)

[T-Bone]

I had no idea you could use require with parenthesis. Lulz. Thanks

And I promise to be a good boy and stop writing .lua in my require functions

[BlackBulletIV]

I had no idea you could use require with parenthesis.

Yeah, it's not a statement. Even if it was, you could still use parenthesis as an expression. For example, this works fine:

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if (hello == 3) then ... end

[Kadoba]

I think this sort of shortcut is limited by a single literal string. It also works with any function.

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print "hi"             -- works
print( "hi" )          -- works
print 4                -- doesn't work
print( 4 )             -- works
print "hi", "there"    -- doesn't work
print( "hi", "there" ) -- works

[bartbes]

I think this sort of shortcut is limited by a single literal string. It also works with any function.

Single is quite redundant, as soon as you start concatenating them it no longer is a literal string, is it?

[XQYZ]

I think this sort of shortcut is limited by a single literal string. It also works with any function.

Single is quite redundant, as soon as you start concatenating them it no longer is a literal string, is it?

What if you assign it to a variable and then use that?

IMHO this whole thing is just inconsistent and Lua should require the brackets all the time. Python had a similar thing in Version 2 where the print command didn't require brackets like all other functions and they dropped that in Version 3 in favor of consistency.

So they should either do that or do it like PHP with their echo command and make it possible to concat strings and variables.

[Kadoba]

What if you assign it to a variable and then use that?

No. It's not a literal anymore then. And yes I agree it's more confusing than useful.

Single is quite redundant, as soon as you start concatenating them it no longer is a literal string, is it?

I mean you can't do this:

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 print "one", "two" 

[slime]

Right, the shortcut only works for a single argument (a literal string or table constructor).

From Programming In Lua:

In both cases, we write a list of arguments enclosed in parentheses. If the function call has no arguments, we must write an empty list () to indicate the call. There is a special case to this rule: If the function has one single argument and this argument is either a literal string or a table constructor, then the parentheses are optional:

[bartbes]

I mean you can't do this:

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 print "one", "two" 

Not. A. Literal.

Also, this is slightly different from your python print (which wasn't a function!), because this works for all functions. ALL.
Same goes for tables, if the only argument is a literal table, you can skip the parentheses (makes a lot more sense than for strings, but whatever).

Right, the shortcut only works for a single argument (a literal string or literal table).

As I said, single literal makes no sense. If you start doing 'operations' on it, it is no longer a literal. It just isn't.