On Sunday, 6 April 2014 at 05:27:44 UTC, Josh wrote:
Can anyone please explain why this works:
auto numbers = sequence!("n")();
auto trimmed = setDifference(setDifference(numbers,
sequence!("n * a[0]")(2)), sequence!("n * a[0]")(3));
but this doesn't?
auto numbers = sequence!("n")();
auto trimmed = setDifference(numbers, sequence!("n *
a[0]")(2));
trimmed = setDifference(trimmed, sequence!("n * a[0]")(3));
Thanks,
Josh
setDifference returns a lazy range, whose type depends on the
inputs. It's not just a generic array. Because of this, while
these *look* like they are just ranges of numbers:
setDifference(numbers, sequence!("n * a[0]")(2));
setDifference(trimmed, sequence!("n * a[0]")(3));
Their *types* and what goes on under the hood is *complelty*
different. Because of this, you can't use the result of the
first, to store the result of the second, the types don't match.
Try this:
auto tmpTrimmed = setDifference(numbers, sequence!("n *
a[0]")(2));
auto trimmed = setDifference(tmpTrimmed, sequence!("n *
a[0]")(3));
