[Python-Dev] Revamping Python's Numeric Model

[Thomas Wouters]

On Sat, Nov 04, 2000 at 09:25:37AM -0600, Charles G Waldman wrote:
> Thomas Wouters writes:

>  > Actually, no, it isn't easily fixable, if at all. The problem is mostly the
>  > scientific notation:

>  > 1.e5

> You could strongly encourage people to spell this 1.0e5

Oh, sure, but that isn't going to solve anything, unless you are proposing
to break the common practice of not requiring zeros before or after decimal
points entirely, and thus breaking gobs of code. The problem is simply that
the syntax is truly ambiguous, and there is no way to tell whether the
statement

  x = 1.e5

is meant to assign 100000 (as a float) to 'x', or assign the 'e5' attribute
of the object '1' to 'x'. Not even full context-based parsing is going to
solve that. This is an edge case, and not likely to happen in real life, but
I don't think it's really worth the trouble, all in all. We'd have to
rewrite the parser into something other than a look-ahead parser to be able
to correctly parse the cases where the syntax isn't really ambiguous, such
as

x = 1.e42e

or some such, and that would still leave unparseable syntax. And all that
just to avoid forcing people to use parentheses around 'normal' integer
literals when directly following them with an attribute dereference. After
all,

 t = 1
 x = t.e5

is perfectly valid, and probably a lot more common. Who needs to run a
method on a literal anyway [don't mention the .join() war!]

-- 
Thomas Wouters <thomas@xs4all.net>

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