Use of "("?) in Lua with string.find and the value that it returns -

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a, i, c = string.find(s, '"("?)', + 1)

what role of ? here? believe checking double quotes not understand use of "("?).

i read string.find returns starting , ending index of matched pattern. per above line of code, a, i , c, 3 values being returned. third value being returned here?

? matches optional character, i.e, 0 or 1 occurrence of character. pattern "("?) matches ", followed optional ", i.e, matches either " or "". note match "?(zero or 1 ") captured.

as return value of string.find(), string.find():

if pattern has captures, in successful match captured values returned, after 2 indices.

the capture third return value, when there successful match.


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