Clearly, that's a bug not a feature. And it should raise an exception - 
the empty string is *not* a valid zero value (but if anyone needs that 
behavior they can handle the exception). About stream rewinding: Doesn't 
matter - I don't think anyone should rely on stream positioning in the 
case of an error.

Cheers,
   - Andreas

nicolas cellier wrote:
> Hello all,
> 
> i noticed that Number readFrom: silently answers 0 when it does not encounter 
> some digits:
> 
>     Number readFrom: '' readStream.
>     Number readFrom: 'foo-bar' readStream.
>     Number readFrom: '.' readStream.
> 
> will all answer 0. Well, i believe there must have been discussions whether or 
> not raising an exception in this case, at least recently in vw list.
> But let us say that answering 0 is a feature.
> 
> 
> Then try:
> 
>     Number readFrom: 'rules are made for the others' readStream.
> 
> fail with an error: 'Invalid radix'.
> Well, well, don't tell me it is a feature.
> 
> 
> And just for fun, this one:
> 
>     Number readFrom: '.e' readStream.
> 
> ah, another feature UndefinedObject doesNotUnderstand: #digitValue.
> 
> 
> Still want to play ? Try this one:
> 
>     Number readFrom: '--1' readStream.
> 
> Amazing what we can do with just one readFrom:...
> 
> 
> Funny, it also accept some un-Smalltalk-ish syntax:
> 
>     Number readFrom: '.1e2'.
>     Number readFrom: '1.e1'.
> 
> will answer a Float (10.0 like FORTRAN).
> I suppose this one is intentionnaly a feature.
> 
> 
> I will not analyze here the cases when the stream advance, and the cases when 
> it does not... That would be boring...
> 
> 
> Now i am trying to implement Float readFrom without accumulating rounding 
> errors, and this can be the right time for deciding about these cases.
> 
> What do you vote for ? exception, answering 0, any other idea ?
> What to do with the stream in case of error ? rewind, keep in place ?
> I'am waiting for your comments.
> 
> Nicolas
> 
> 
>