Creating a calculator

[Antoon Pardon]

Op 01-07-16 om 15:52 schreef Steven D'Aprano:
> On Fri, 1 Jul 2016 10:25 pm, Christopher Reimer wrote:
>
>> For my BASIC interpreter, each line of BASIC is broken this way into
>> tokens.
> [...]
>> By using * to unpack the split line, my program no longer crashes and no
>> try/except block is needed to work around the crash. A later line of code
>> will test the expression, ignore if empty or run regex if full.
> I wish you wouldn't describe this as "crash".

I wish you wouldn't mix semantic levels.

>
> The Python interpreter should never crash. That would be a segmentation
> fault, and that is considered to be a very serious bug.

But in that case your computer didn't crash. That would be a your computer
freezing, or rebooting.

>
> But *raising an exception* is another story. Raising exceptions is not a
> crash, it is the interpreter working as expected. This statement:

A segment violation is not a crash either, your computer/os will just
carry on.

>
>     line_number, keyword, expr = "20 END".split(' ', 2)
>
> is SUPPOSED to raise an exception, if it didn't, the interpreter would be
> broken. To call that a "crash" is horribly misleading.

Supposed by whom? The line may be supposed to raise an exception by
the languager designer, that doesn't mean the programmer meant to
write an instruction that would raise an exception. So the programmer
can correctly assert the line was not supposed to raise an exception.

-- 
Antoon.