I know that D2 is supposed to be closed for new features, but I thought
I'd mention this anyway just in case it's deemed easy/simple enough for
inclusion, or even if it will just get considered for later on.
Anyway, we all know that we can do the following:
foreach (int x; 0..10)
writeln(x);
That will print 0, 1, 2 .. 9.
We could also write it like this:
foreach (int x; iota(0, 10))
writeln(x);
for the same effect.
If we want only odd numbers then we can use:
foreach (int x; filter!("a & 1")(iota(0, 10)))
writeln(x);
but what we cannot write is:
foreach (int x; filter!("a & 1")(0..10))
writeln(x);
because 0..10 isn't a range literal -- it's a special notation that only
applies to foreach loops and array slicing.
Proposal: Make a..b a literal that evaluates to iota(a, b) or some
built-in equivalent. Of course, the $ symbol would not be valid for
these literals.
More advanced proposal: Make .. into a binary operator, which is
language-defined for integer data types (takes two integers, returns
iota), and overloadable for user data-types. Why would you want to
overload it? For linked data-structures, it would be an ideal candidate
for creating a range between two links (linkA..linkB).
Pros
----
- Creates more uniformity and purity across the language i.e. if I can
use X and Y to the same effect (as above) then I expect f(X) and f(Y) to
have the same effect -- assuming that f is referentially transparent.
- Adds a nice, intuitive shorthand for a common practice, increasing the
productivity and readability of D code.
- It removes a special case of foreach.
- Doesn't (shouldn't?) break backwards-compatibility. If reliance on
std.algorithm.iota is a problem then perhaps it would be best encoded as
a D runtime type.
Cons
----
- Slicing still remains a special case, which might confuse people into
thinking that slicing is an operation that takes a range (arguably, this
is already the case)
- Requires core language and compiler changes.
I also have a proposal for slicing along the same lines, but I'll leave
that for later.
