Le 19/02/2013 07:09, monarch_dodra a écrit :
On Tuesday, 19 February 2013 at 10:37:31 UTC, n00b wrote:
Hello.
------
MyType increment(MyType previous)
{
//snip
}
auto myRec = std.range.recurrence!increment(initialMyType);
-----
... doesn't work. What am I doing wrong? The documentation doesn't
seem to imply the function has to be passed as a string, if that's the
issue.
It is not very well documented (or should I say, documented at all...),
but the signature of a recurrence function must take the form:
"auto recurrence(R)(R r, size_t n);"
Where:
n is the current index being calculated and:
r is a range that holds the values of your recurrence, and is valid for
the indices "n - 1" to "n - numberOfInitialArgs". The type of R is
implementation defined. (It's a "Cycle!(T[Args.length])" for efficiency
reasons, fyi, but this is an implementation detail).
For example, fibs and ! would be implemented as such:
//----
import std.stdio;
import std.range;
int fibFun(R)(R r, size_t n)
{
return r[n - 1] + r[n - 2];
}
int expFun(R)(R r, size_t n)
{
return n * r[n - 1];
}
void main()
{
//auto myRec = std.range.recurrence!(increment)('a', 'b');
auto fib = std.range.recurrence!fibFun(1, 1);
auto exp = std.range.recurrence!expFun(1);
writeln(fib.take(10));
writeln(exp.take(10));
}
//----
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
[1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
//----
Thanks a lot. I reported the lack of documentation to bugzilla, I hope I
did it right...^^
