In transforming dates through a Lua-call I get a nil error I do not understand.
The luatex code =
\startluacode
hvdm = hvdm or {}
require "lpeg"
-- Transform date in Lua from yyyymmdd to dd-mm-yyyy with checks
hvdm.day = lpeg.R("02") * lpeg.R("09") + lpeg.P("30") + lpeg.P("31") -
lpeg.P("00")
hvdm.month = lpeg.P("0") * lpeg.R("19") + lpeg.P("10") + lpeg.P("11") +
lpeg.P("12")
hvdm.year = lpeg.R("12") * lpeg.R("09") * lpeg.R("09") * lpeg.R("09")
hvdm.date = lpeg.C(hvdm.year) * lpeg.C(hvdm.month) * lpeg.C(hvdm.day) *
-1 / "%3-%2-%1"
\stopluacode
\def\FormatDate#1{\ctxlua{tex.print(tostring(hvdm.date:match(#1)))}}
Calling \FormatDate(1) is OK although it returns "nil" (correct would be #1 =
20101114
Calling \FormatDate(A) is not OK with the error:
! LuaTeX error <main ctx instance>:1: bad argument #1 to 'match' (string
expected, got nil)
stack traceback:
[C]: in function 'match'
<main ctx instance>:1: in main chunk.
It is no problem if the function returns the string "nil" from tostring() but
an error like this I would like to avoid.
Hans van der Meer
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