Re: A little bit of golf

[Jonathan Goble <jcgoble3@...>]

On Tue, Apr 7, 2015 at 8:12 PM, Hisham <h@hisham.hm> wrote:
>    -- At your discretion: how to deal with...
>    -- "$fooend"
>    -- "${}"
>    -- "${bo{bozo}zo}"
>    -- "${bo${bar}zo}"


I set up the following test cases for those, plus two more:

{ from = "$fooend", to = "$fooend" }, -- ignore undefined vars
{ from = "${}", to = "${}" }, -- ignore empty braces
{ from = "${bo{bozo}zo}", to = "${bo{bozo}zo}" }, -- too weird, ignore
{ from = "${bo${bar}zo}", to = "${bofoozo}" }, -- expand the innermost one
{ from = "test ${foo", to = "test ${foo" }, -- ignore unclosed braces
{ from = "test $bar}bar", to = "test foo}bar" }, -- don't strip the stray brace


With those and the variables and test cases you defined, this shorter
function passes all tests:

local function expand_variables(str)
    return str:gsub("%$(%{?)([A-Za-z0-9_]+)(%}?)", function(open, var, close)
        if #open == 1 and #close == 0 or not variables[var] then
            return "$"..open..var..close
        else return variables[var] .. (#open == 0 and close or "")
    end end)
end

Of course, I could have explicitly checked for open == "{", etc., but
#open == 1 is one keystroke shorter, and this is golf. :-)

Jonathan