Match for several symbols in char-set

Question

Lua's (and any other regex I think) have char-sets that allow matching for any symbol in the set. Is there a way to match several symbols from that set as one? Example

text:gsub("foo[^bar]-","") -- matches for any foo that is not followed by 'b', 'a' or 'r'

Is there a way to make it allow 'b', 'a' or 'r', but not allow exactly 'bar' (and maybe a few more non-one symbol) patterns after?

Lua patterns are poor at checking multicharacter contexts. What is your real life problem? — Wiktor Stribiżew, Dec 21 '20 at 18:00
@WiktorStribiżew I am adjusting Aegisub script, it has pattern like `:gsub("(\\r[^}]-)}","%1\\alpha&H"..al.."&}")` which check for `\r` that does not end the tag. I would like it to check that it's `\r` that is not followed by `\alpha` tag. (so `\r\alpha` should not be matched) — IAmVisco, Dec 21 '20 at 18:02

score 1 · Accepted Answer · answered Dec 21 '20 at 18:40

local s = "{aaa\\rbbb} {ccc\\r\\alpha} {eee\\r}"
print(s)

local s1 = s:gsub("(\\r[^}]-)}","%1\\alpha&H&}")
print(s1)

local s2 = s:gsub("\\alpha", "\0%0")  -- insert zero byte before each \alpha
            :gsub("(\\r%f[^r%z][^}]*)}", "%1\\alpha&H&}")
            :gsub("%z", "")           -- remove all zero bytes
print(s2)

Output:

{aaa\rbbb} {ccc\r\alpha} {eee\r}
{aaa\rbbb\alpha&H&} {ccc\r\alpha\alpha&H&} {eee\r\alpha&H&}
{aaa\rbbb\alpha&H&} {ccc\r\alpha} {eee\r\alpha&H&}

Adjusted a bit since `\r` can have more stuff after it and it works like a charm! Thanks. — IAmVisco, Dec 21 '20 at 19:34

Match for several symbols in char-set

1 Answers1