Re: On adding type information to a dynamically typed language
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- Subject: Re: On adding type information to a dynamically typed language
- From: Luiz Henrique de Figueiredo <lhf@...>
- Date: 2017年9月20日 08:28:58 -0300
> is = setmetatable ({ }, {
> __index = function (_, TYPE)
> return function (VALUE)
> assert (type (VALUE) == TYPE)
> return VALUE
> end end })
>
> and use
> f (is.number (x), is.string (s))
> which looks a lot better, without any patching.
This is nice but creates lots of functions. Here is an alternative:
local types = {
"nil", "boolean", "number", "string", "table", "function", "userdata", "thread",
}
is = {}
for _,t in pairs(types) do
is[t] = function (v)
if type(v)~=t then
error(t.." expected, got "..type(v),2)
end
return v
end
end
function f() end
x=2
s="a"
s=2
f (is.number (x), is.string (s))