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local re = require 'relabel'
local g = re.compile[[
S <- Id List
List <- !. / Comma Id List
Id <- Sp [a-z]+ / %{ErrId}
Comma <- Sp ',' / %{ErrComma}
Sp <- %s*
]]
function mymatch (g, s)
local r, e, pos = g:match(s)
if not r then
local line, col = re.calcline(s, pos)
local msg = "Error at line " .. line .. " (col " .. col .. ")"
if e == 'ErrId' then
return r, msg .. ": expecting an identifier before '" .. s:sub(pos) .. "'"
elseif e == 'ErrComma' then
return r, msg .. ": expecting ',' before '" .. s:sub(pos) .. "'"
else
return r, msg
end
end
return r
end
print(mymatch(g, "one,two"))
print(mymatch(g, "one two"))
print(mymatch(g, "one,\n two,\nthree,"))
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