lualua-patterns

capture word a or b and part of optional extra arguments


First of all this doesn't match ok or capture "ok".find("(ok|capture)") -- nil

Second, followed by ok match an optional ok;args but only capture args as parameter. This is wrong "ok;args".find("(ok)(;.+)?"), and capture group includes extra ;.

function mymatch(str)
  local _, _, ok, oreveal = str:find("(ok)")
  return ok, oreveal
end

-- this is what I want
print(mymatch("ok")) -- ok nil
print(mymatch("cancel")) -- cancel nil
print(mymatch("ok;domatch")) -- ok domatch
print(mymatch("okdontmatch")) -- nil nil

Solution

  • You can use

    function mymatch(str)
      local _, _, ok, oreveal = str:find("^(ok%f[%A]);?(.*)$")
      if ok == nil then
        _, _, ok, oreveal = str:find("^(cancel%f[%A]);?(.*)$")
      end
      if oreveal == "" then
        oreveal = nil
      end
      return ok, oreveal
    end
    
    -- this is what I get
    print(mymatch("ok")) -- ok nil
    print(mymatch("cancel")) -- cancel nil
    print(mymatch("ok;domatch")) -- ok domatch
    print(mymatch("okdontmatch")) -- nil nil
    

    See the online Lua demo.

    The ^(ok%f[%A]);?(.*)$ pattern matches

    • ^ - start of string
    • (ok%f[%A]) - Group 1: ok and a trailing "word boundary" (%f[%A] is a frontier pattern making sure that the next char if present must be a non-letter)
    • ;? - an optional ;
    • (.*) - Group 2: the rest of the string
    • $ - end of string.