throw vs the result

[J. Landman Gay]

On 4/30/05 11:27 PM, Phil Davis wrote:

> Dar Scott wrote:
> 
>> OK, well, what about a library that exports lots of functions, such as 
>> a math library?  Functions don't have a separate result for an error.
>>
>> Should the error be a special value in the result and propagated through?
>> Or should an error function tell whether there was an error since the 
>> last call to error function?
>> Or should an error be thrown?
> 
> 
> 
> I like the 'special value' idea.
> 
> What if the last (or first?) param passed to the function by my script 
> is the value to be returned to my script if an error occurs?

The HyperCard standard for this was to preceed the value with a special 
string, commonly "Error:". Then your handler just checks to see if word 
1 is that string.

put myFunction() into tValue
if word 1 of tValue = "Error:" then
   -- something went wrong; check the rest of the string
else
   -- do your thing
end if

Not fancy, but it works.


-- 
Jacqueline Landman Gay         |     jacque at hyperactivesw.com
HyperActive Software           |     http://www.hyperactivesw.com