[Python-Dev] Lukewarm about range literals

[Tim Peters]

[Skip Montanaro]
> ...
> What we really want I think is something that evokes the following in the
> mind of the reader
>
>     for i from START to END incrementing by STEP:
>
> without gobbling up all those keywords.

Note that they needn't be keywords, though, any more than "as" became a
keyword in the new "import x as y".  I love the Haskell notation in Haskell
because it fits so nicely with "infinite" lists there too.  I'm not sure
about in Python -- 100s of languages have straightforward integer index
generation, and Python's range(len(seq)) is hard to see as much more than
gratuitous novelty when viewed against that background.

    for i = 1 to 10:           #  1 to 10 inclusive
    for i = 10 to 1 by -1:     #  10 down to 1 inclusive
    for i = 1 upto 10:         #  1 to 9 inclusive
    for i = 10 upto 1 by -1:   #  10 down to 2 inclusive

are all implementable right now without new keywords, and would pretty much
*have* to be "efficient" from the start because they make no pretense at
being just one instance of an infinitely extensible object iteration
protocol.  They are what they are, and that's it -- simplicity isn't
*always* a bad thing <wink>.

>     for i in [START..END,STEP]:
>     for i in [START:END:STEP]:
>     for i in [START..END:STEP]:

The difference in easy readability should squawk for itself.

>     for i in 0 ..! len(a):
>         a[i] += 1

Looks like everybody hates that, and that's understandable, but I can't
imagine why

     for in 0 .. len(a)-1:

isn't *equally* hated!  Requiring "-1" in the most common case is simply bad
design.  Check out the Python-derivative CORBAscript, where Python's "range"
was redefined to *include* the endpoint.  Virtually every program I've seen
in it bristles with ugly

    for i in range(len(a)-1)

lines.  Yuck.

but-back-to-2.0-ly y'rs  - tim