buildpath

function buildpath(from, to, sepChar)
--
-- if no command separator character is specified, use default.
local sep  = sepChar or zs.func.char( zs.func.pref( 'iSepChar' ) )
--
zs.var.fromroom = from
zs.var.toroom   = to
--
local sw = zs.func.pathfrom( from, to )
--
zs.var.rawsw = sw
--
local C, Cc, Cf, P, V, match = lpeg.C, lpeg.Cc, lpeg.Cf, lpeg.P, lpeg.V, lpeg.match
--
local directions, portal, sw_e, sw_s, walk = V( 'directions' ), V( 'portal' ), V( 'sw_e' ), V( 'sw_s' ), V( 'walk' )
--
local run = function( sw ) if sw:len() > 1 then sw = "run "..sw end return sw end
--
local fold = function( walk, sw )
--
    if walk:len() == 0 then return sw end
--
    if sw:len() == 0 then return walk end
--
    return walk..sep..sw
--
end
--
local speedwalk = P {                                                                   -- grammar for path decoding.
                      'speedwalk',                                                      -- starting symbol name.
                      sw_e       = P(sep),                                              -- end-of-speedwalk   marker.
                      sw_s       = P('.'),                                              -- start-of-speedwalk marker.
                      directions = C((1 - sw_e)^0),                                     -- speedwalk string capture.
                      portal     = P('(' * C((1 - P(')'))^1) * ')')^0,                  -- custom exit command capture.
                      walk       = sw_s * portal * (directions / run) * sw_e^-1,        -- speedwalk iteration element.
                      speedwalk  = Cf(Cc("") * walk^0, fold)                            -- complete speedwalk search pattern.
                    } * -1                                                              -- end-of-input marker.
--
return match( speedwalk, sw )
--
end