Re: String-to-number coercion

[Mike Nelson <mikestar1313@...>]

On 9/15/2013 5:26 PM, Luiz Henrique de Figueiredo wrote:
> > 2013/9/10 Andrew Starks <andrew.starks@trms.com>:
> >
> > > In my very humble opinion (and despite my own transgressions into
> > > discussions on its redesign :), it gets this balance perfectly... Except
> > > when it prompts strings to numbers. .)
> > More precisely: the exact spot where this irks me is that if you set
> > metamethods for str:__add etc, they don't get invoked when tonumber()
> > succeeds for both operands, EVEN WHEN BOTH ARE STRINGS.
> Wthat do you mean, exactly? Can you please give an example?
debug.setmetatable("",{
__add=function()
error("can't add strings, you know") end})

print("1"+"2")


this prints 3 rather than raising an error.


change the last line to print("1"+"ZZ")

and the error in the above metatable is raised, rather than the standard 
"attempt to perform arithmetic on a string value".