Re: Data transformation templates
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- Subject: Re: Data transformation templates
- From: Javier Guerra Giraldez <javier@...>
- Date: Wed, 8 Jan 2014 08:52:06 -0500
On Wed, Jan 8, 2014 at 8:16 AM, Alexander Gladysh <agladysh@gmail.com> wrote:
> I'd like to write this declaratively. Maybe like this:
>
> local result = T:map (data)
> {
> sprite = "/img/" .. T(1);
> x = T(2), y = T(3);
> }
what's wrong with the classic map(t,f) transformation?
function map(t,f)
local o={}
for i = 1,#t do
o[i] = f(t[i])
end
return o
end
local result = map(data, function(e) return {
sprite = '/img/'..e[1],
x = e[2], y = e[3]
})
i guess for complex mappings a naïve map(t,f) doesn't cut it, but a
template wouldn't either....
or maybe you want to do it at compile time to avoid runtime delay? i
typically get it just by calling any startup transformation on the
module itself, not on any function.
or you just want very high performance, avoiding the n function calls
overhead? i've done simple things like:
function buildmap(b)
return loadstring([[
function (t)
local o = {}
for i = 1, #t do
local in,out = t[i], nil
]]..b..[[
o[i] = out
end
return o
]])
end
buildmap([[
out = {
sprite = '/img/'..in[1],
x = in[2], y = in[3]
}
]])(data)
but i don't like it...
--
Javier