Re: error() or nil, 'error msg'
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: error() or nil, 'error msg'
- From: Tim Hill <drtimhill@...>
- Date: 2014年9月24日 11:53:35 -0700
On Sep 24, 2014, at 9:22 AM, Tom N Harris <telliamed@whoopdedo.org> wrote:
> On Tuesday, September 23, 2014 01:09:36 PM Daurnimator wrote:
>> This seems to be asking for some form of selective 'catch'.
>> (as in, try{} catch(Exceptions.NOMEM) {}
>
> Not sure I like the attempt to sneak static typing into a dynamic language.
>
> I tried thinking of some way to reduce the boilerplate needed to handle erros
> but what I thought of basically boiled down to
>
> local this,errmsg = dosomething()
> if not this then
> -- handle error with errmsg
> end
>
What about pairing an error handler and a function using a closure factory?
-- Wrap a function f with a paired error handler eh
function errorwrap(f, eh)
return function(...)
local t = table.pack(f(...))
if t[1] then return table.unpack(t) else return eh(f, t) end
end
end
-- A function to wrap
function myfunc(x)
if x < 0 then return nil, "must be positive" else return x end
end
-- An error handler: f=function, r=return values
function eh1(f, r)
print("error in " .. tostring(f) .. ": " .. r[2])
end
local mywrappedfunc = errorwrap(myfunc, eh1)
mywrappedfunc(5)
mywrappedfunc(-5)
Can also be used to wrap pcall() to catch functions that throw errors.
—Tim