On 09/08/2019 12:50:14, Steven D'Aprano wrote:
On Thu, Aug 08, 2019 at 04:28:28PM -0700, Barry Warsaw wrote:
I find it difficult to imagine a more meaningful distinction than that
between syntax and semantics.
The distinction between syntax and semantics can sometimes be blurred.
Certainly in spoken languages. What about program code?
Should x/0 be a SyntaxError? It too is "disallowed", and we have to
change our code.
No, because x might be an instance of a class (extended numbers?) that
allows division by zero.
Should None[x] be a SyntaxError? It too is "disallowed", and we have to
change our code.
It's allowable syntax with defined runtime semantics: raise a TypeError
if x exists,
and a NameError if it isn't. Conceivably some programmer might find a
use for it.
But since it always raises an exception, it would probably be more
helpful in the long
run if it *were* a SyntaxError. It *isn't*, because (I assume)
detecting this and similar
idioms, e.g. {}[0] , would complicate the parser/compiler too much.
Your examples show, I claim, that even in program code the distinction
between
syntax and semantics is not always obvious.
I suggest the only watertight definition of a syntax error is something
which raises
an exception at compile time. Obviously this can depend not only on the
code,
but also on the compiler.
Rob Cliffe
_______________________________________________
Python-Dev mailing list -- python-dev@python.org
To unsubscribe send an email to python-dev-le...@python.org
https://mail.python.org/mailman3/lists/python-dev.python.org/
Message archived at
https://mail.python.org/archives/list/python-dev@python.org/message/FKZSJS2JZ3DXENYOI3AFPGDH3TOH5C5U/
