On 8/19/14, Stephan Hennig <[log in to unmask]> wrote:

> Am 19.08.2014 um 19:21 schrieb Heiko Oberdiek:

>

>>> \ExplSyntaxOn

>>> \directlua{

>>>   local myarg = '\mymacro'

>>>   texio.write_nl('l3: argument is ' .. tostring(myarg))

>>> }

>>> [...]

>>> First, spaces are gone in Lua code.  Though, spaces are significant in

>>> Lua.

>>

>> `\ExplSyntaxOn' says that spaces are gone, that's the purpose of this

>> command. Explicit spaces are available via `~':

>

> Have already seen that when using l3's message mechanism, but didn't try

> in \directlua.  Thanks!

>

>

>>> Second, variable myarg is nil with \ExplSyntaxOn.  (I don't understand

>>> why.)

>>

>> Without spaces you get:

>>

>>   localmyarg='\mymacro'

>

> Should have seen that by myself.  Thanks again!

>

>

>> BTW, this is quite a risky way to pass the contents of user variables ot

>> Lua code. Consider syntax errors, if "\mymacro" contains ', or

>> "\mymacro" could even contain containing something like:

>>    '; very evil code; local dummy='

>>

>> There is \luaescapestring/\luatexluaescapestring:

>>

>>   '\luatexluaescapestring{\mymacro}'

>

> It's actually a language string that I'm evaluating to a number via

>

>   \the\csname l@#1\endcsname       or

>   \int_use:N\cs:w l@#1\cs_end:     in LaTeX3

>

> If #1 contains no valid language identifier, the expression should throw

> an error.  So, I think I'm safe here.  I'm indeed using \luaescapestring

> in other circumstances.

>

> Thanks!

> Stephan Hennig



Avoid using \cs:w ... \cs_end: constructions.  It is much better to

use a c-type argument, so for your case, \int_use:c { l@#1 }.



Regards,

Bruno