In addition to defying the ordinary order of the syntax, that would make this statement totally ambiguous: [f(x), f(y) for x in list1 for y in list2, while x < y] And I definitely don't think commas (other than the f(x), f(y) usage shown above) or semicolons are good ideas. On Mon, Jul 1, 2013 at 10:53 PM, SpaghettiToastBook . < spaghettitoastbook@gmail.com> wrote:
What if the while clause went after the rest of the comprehension, preceded by a comma?
[f(x) for x in list, while x < 10]
— SpaghettiToastBook
On Mon, Jul 1, 2013 at 10:28 PM, Daniel Robinson <gottagetmac@gmail.com> wrote:
While this looks attractive to me, and it's definitely better to change statement and comprehension syntax at the same time, this makes the comprehension ambiguous to human parsing.
[f(x) for x in list if x > 10] basically can be read as
for x in list: if x > 10: f(x)
This kind of interpretation becomes critical if you nest more than two levels. But [f(x) for x in list while x < 10] could read either as
for x in list while x < 10: f(x)
which is how you want it to be read, or (more in line with earlier list comp habits):
for x in list: while x < 10: f(x)
which would be totally wrong.
I don't think this is a very serious problem (certainly not for the interpreter), but it's a stumbling block.
On Mon, Jul 1, 2013 at 10:03 PM, Jan Kaliszewski <zuo@chopin.edu.pl> wrote:
2013-07-02 00:44, Oscar Benjamin wrote: [...]
Having a while clause on for loops is not just good because it saves a couple of lines but because it clearly separates the flow control from the body of the loop (another reason I dislike 'break if'). In other words I find the flow of the loop
for p in primes() while p < 100: print(p)
easier to understand (immediately) than
for p in primes(): if p >= 100: break print(p)
+1
Cheers. *j
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