• n00b (10/10) Feb 19 2013 Hello.
• monarch_dodra (36/47) Feb 19 2013 It is not very well documented (or should I say, documented at
• n00b (3/51) Feb 19 2013 Thanks a lot. I reported the lack of documentation to bugzilla, I hope I...

n00b <n00b nospam.com> writes:

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.

"monarch_dodra" <monarchdodra gmail.com> writes:

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]
//----

n00b <n00b nospam.com> writes:

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...^^