Re: Attempt to perform arithmetic on a string value

[Ben Sunshine-Hill <bsunshin@...>]

The only way to do that automatically would be to modify the Lua source code. 
At a quick glance, it looks like the best place to make lua accept the empty 
string as 0 would be to modify lobject.c, changing luaO_str2d as follows 
(under 5.0): change 

if (endptr == s) return 0;  /* no conversion */

to

if (endptr == s && *endptr) return 0;  /* no conversion */

Code barely tested. Caveat emptor.

Ben

On Sunday 28 March 2004 10:09 pm, Stoil Todorov wrote:
> Thank You, but I want when there are arithmetic
> operation with string and number, and if the string is
> empty, the result to be 0/zero/ or ""/empty string/.
>
> --- RLake@oxfam.org.pe wrote:
> > > Could someone tell me how to avoid the error,
> >
> > wchich
> >
> > > LUA sends when it performs arithmetic operation
> >
> > with
> >
> > > empty string value.
> >
> > Consider changing the logic of your program so that
> > the
> > initial value of A2.value is 0 instead of "" ?
> >
> > Otherwise, try this:
> >
> > function optnumber(s)
> >   return tonumber(s) or (s == "" and 0) or
> > error("expected number, got
> > "..type(s))
> > end
> >
> > or some other variation on the theme.
>
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-- 
Ben Sunshine-Hill
Student and Programmer
Your lucky words for today: campfire, bridegroom, and scornfully.