Example of a lua DSL language

dsl-print

#!/usr/bin/env lua
--[[
dsl-print [some.dsl]

Example of a lua DSL language, that can use function call or assignment to define
keys, and uses call sequence to implicitly define nesting.
]]

function dsl(code, file)
    local loaded, estr = loadstring(code, file)

    if not loaded then
        return nil, estr
    end

    local _sections = { file = file };
    local _section
    local _links
    local _link

    local G = {
        BeginSection = function(section)
            _section = { section = section }
            _links = {}
            _section.links = _links
            table.insert(_sections, _section)
        end;
        EndSection = function()
            _section = nil
        end;
        Link = function(link)
            _link = { link = link }
            table.insert(_links, _link)
        end;
        href = function(href)
            _link.href = href
        end;
        title = function(title)
            _link.title = title
        end;
    }
    local env = setmetatable({}, {
        __index = function(t, k)
            return G[k]
        end;
        __newindex = function(t, k, v)
            if G[k] then
                G[k](v)
            else
                rawset(t, k, v)
            end
        end;
    })

    setfenv(loaded, env)

    local ok, estr = pcall(loaded)

    if not ok then
        return nil, estr
    end

    return _sections
end

function dump(t, lead)
    lead = lead or ""
    for k,v in pairs(t) do
        if type(v) == "table" then
            if type(k) == "number" then
                k = "["..k.."]"
            end
            print(lead..k.." =")
            dump(v, lead.."  ")
        else
            print(lead..k.." = "..tostring(v))
        end
    end
end

file = "(--)"
code = [[
BeginSection "news"
  Link "C-programming"
    href = "etc."
    title "a book on C"

  Link = "I love lua"
    href "etc."
    title = "an essay"
BeginSection "other"
  Link "yes, yes" href = "http..." title = "a title"
-- Because you can't have a call or assignment with no argument, either remove
-- EndSection from your language (its unnecessary), or call it with an
-- argument.
EndSection ""
]]

if arg[1] then
    file = arg[1]

    local f = assert(io.open(arg[1], "r"))
    code = f:read"*a"
end

t = assert(dsl(code, file))

dump(t)