Re: A little bit of golf

[William Ahern <william@...>]

On Wed, Apr 08, 2015 at 12:13:17AM -0400, Rena wrote:
> On Tue, Apr 7, 2015 at 11:06 PM, Andrew Starks <andrew.starks@trms.com> wrote:
> >
> >
> > On Tuesday, April 7, 2015, Sean Conner <sean@conman.org> wrote:
> >>
> >> It was thus said that the Great Daurnimator once stated:
> >> > On 8 April 2015 at 10:12, Hisham <h@hisham.hm> wrote:
> >> > > Ah! NO LPEG ALLOWED! :)
> >> >
> >> > Why not?
> >>
> >>   Way too easy.
> >>
> >>         lpeg = require "lpeg"
> >>         id = lpeg.R("AZ","az","09","__")^1 / variables
> >>         expand_variables = lpeg.Cs((
> >>                    (lpeg.P"${") / "" * id * (lpeg.P"}"/"")
> >>                  + (lpeg.P"$")  / "" * id
> >>                  + lpeg.C(lpeg.P(1))
> >>                )^0)
> >>
> >>   -spc (Could be made even smaller ... )
> >
> > Right. Too easy and too readable. :)
> >
> > -Andrew
> 
> That's your idea of readable? Yikes.
> 
> Maybe not shortest, but somewhat clear solution:
> local vars = setmetatable({foo="bar"}, {
>     __index = function(self, k)
>         return type(k) == 'string' and rawget(self, k:match('{?([%w_]+)}?'))
>     end,
> })
> function expand_variables(str)
>     return str:gsub('%$(%S+)', vars)
> end

Now modify yours to support escaping $, like "Hello \$planet!". Note should
also permit escaping the escape character, "Hello \\$planet!".