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If line 9 of the program is commented out, it runs fine.
Otherwise lots of error messages which don't pan out for me.
I tried changing Negative.front to be const, which didn't help.
I am not quite sure what the error messages are telling me.
Thank you for your assistance!
C:\D\dmd2\windows\bin64\..\..\src\phobos\std\range\package.d(4560): Error: mutable method `app.Negative!(Take!(FibonacciSeries)).Negative.front` is not callable using a `const` object
return _current.front;
^
c:\dev\D\81 - 90\c82_1e_InputRange_does_support_cycle_with_save\source\app.d(44): Consider adding `const` or `inout` here
auto front()
^
C:\D\dmd2\windows\bin64\..\..\src\phobos\std\range\package.d(4695): Error: template instance `std.range.Cycle!(Negative!(Take!(FibonacciSeries)))` error instantiating
else return Cycle!R(input);
^
c:\dev\D\81 - 90\c82_1e_InputRange_does_support_cycle_with_save\source\app.d(9): instantiated from here: `cycle!(Negative!(Take!(FibonacciSeries)))`
.cycle // ← compilation ERROR
^
source/app.d
import std.stdio;
import std.range;
void main()
{
writeln(FibonacciSeries()
.take(5)
.negative
.cycle // ← compilation ERROR
.take(10));
}
struct FibonacciSeries
{
int current = 0;
int next = 1;
enum empty = false;
int front() const
{
return current;
}
void popFront()
{
const nextNext = current + next;
current = next;
next = nextNext;
}
FibonacciSeries save() const
{
return this;
}
}
struct Negative(T) if (isInputRange!T)
{
T range;
bool empty()
{
return range.empty;
}
auto front()
{
return -range.front;
}
void popFront()
{
range.popFront();
}
static if (isForwardRange!T)
{
Negative save()
{
return Negative(range.save);
}
}
}
Negative!T negative(T)(T range)
{
return Negative!T(range);
}
