spir:
> Sorry, but you are wrong on this. I understand this sounds unsafe, but no.
> Most
> languages, I guess, just do that without any worry. In particular, I have
> frequented python and Lua mailing lists for years without even reading once
> about this beeing a misfeature (and indeed have never run into a bug because
> of
> this myself). It is simply the right semantics in 99.999% cases.
Thank you for raising this topic again. I have raised it probably more than one
year ago, and all people around here were against this. This is not unsafe,
it's actually safer than the current D behaviour. Python designers don't think
this is a badly designed part of Python, they think this is as desired, and I
too have never seen people complain about this being a bad or bug prone design.
An example of Python code:
s = "abcdefg"
upper = 20
s2 = s[2 : upper]
assert s2 == "cdefg"
Equivalent D2 code, if you forget to use the min() you are doomed:
import std.algorithm: min;
void main() {
string s = "abcdefg";
int upper = 20;
string s2 = s[2 .. min($, upper)];
assert(s2 == "cdefg");
}
The saturating nature of Python slice bounds is a safety net that's useful to
avoid some troubles. The only good thing of the D2 design is that it performs
less tests at runtime (it has no need to call min() in general), this is a bit
positive in a system language, but in this case it has a cost in safety.
Bye,
bearophile
