Lua: Replace characters in a string

Question

I have strings like

abcdef
abcd|(
abcde|(foo 
abcd|)
abcde|)foo

which should be modified to

abcdef
abcd
abcde \foo 
abcd
abcde \foo 

• if there is no | then do nothing
• if nothing follows the |( or |) then delete these two characters
• if something follows then replace |( or |) with <space>\

I am interested in short pattern expressions, if possible. I can do this by several string.find and string.sub but then I have a lot of if statements.

Answer 1

You may use

function repl(v)
    res, _ = string.gsub(v:gsub('|[()]$', ''), '|[()]', ' \\')
    return res
end

See Lua demo online

Details

• '|[()]$' matches | and then either ( or ) at the end of the string, and string.gsub replaces these occurrences with an empty string
• |[()] then matches | and then either ( or ) anywhere in the string, and string.gsub replaces these occurrences with a space and \.