shortest distance between line and point

[bobpit]

It is a classic problem/algorithm.  I am trying to find something in AFL but I can't.

What I really want to do is implement the Ramer–Douglas–Peucker algorithm (description and pseudocode here:  en.m.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm  ).

It I could not find code for the entire algorithm, but I am hoping to find for the shortestDistanceToSegment(..).

[bobpit]

good old google:
en.wikipedia.org/wiki/Distance_from_a_point_to_a_line

Now I am looking for something more difficult: A NON-recursive implementation of the Ramer–Douglas–Peucker algorithm. The classic algorithm is recursive, and AFL does not support it.

[fxshrat]

Of course AFL supports recursive formulas.

[bobpit]

".... recursion (having a function call itself from within itself) is NOT supported as for now."
www.amibroker.com/guide/a_userfunctions.html


Maybe we are talking about different things?  Couple of days ago I tried recursion and it did not work.  Could you send me a very small afl code that uses recursion?

[fxshrat]

Recursion is achieved via loop or in some cases AMA, AMA2, Valuewhen, Cum

Loop example


_Z = 0; // initialize

for ( i = 1; i < BarCount; i++ )
{
   prev = _Z[ i - 1 ]; // PREV is previous value of _Z.
   _Z[ i ] = 0.4 * A[ i ] + 0.6 * prev;
}


AMA2 example doing same as upper loop.
_Z = AMA2( _A, 0.4, 0.6 );

[fxshrat]

Another recursive ( self-referencing) loop example

x = 0;
for ( i = 1; i < BarCount; i++ )
{
   x[ i ] = IIf ( C[ i ] > x[ i - 1 ], C[ i ], x[ i - 1 ] );
}

That can be replaced by simple array function

x = Highest( C );

[fxshrat]

The link in reply #3 says

Note also that recursion (having a function call itself from within itself) is NOT supported as for now.

AFAIU it means something like this
function myfunc( per )
{
  array = myfunc( 10 );
  return array*C;
}

No?

[bobpit]

Yes, it seems we are talking about different things. In your example I have not seen "a function call itself from within itself".

This is the classic recursion example, the factorial (in C, taken from www.programiz.com/c-programming/examples/factorial-recursion  ):

int factorial(int n)
{
if(n!=1)
return n*factorial(n-1);
}

This is the one I failed to do in AFL. You say it is possible to do it in AFL?

[bobpit]

May 24, 2015 20:44:58 GMT fxshrat said:

function myfunc( per )
{
  array = myfunc( 10 );
  return array*C;
}

No?

YES!  and the above code cannot run in AFL.

[fxshrat]

May 24, 2015 20:48:03 GMT bobpit said:

Yes, it seems we are talking about different things. In your example I have not seen "a function call itself from within itself".

This is the classic recursion example, the factorial (in C, taken from www.programiz.com/c-programming/examples/factorial-recursion  ):

int factorial(int n)
{
if(n!=1)
return n*factorial(n-1);
}

This is the one I failed to do in AFL. You say it is possible to do it in AFL?

Of course you can do factorial in AFL

function factorial( f )
{
   result = f;
   for ( i = f - 1;i >= 1;i-- )
       result *= i;
   return result;
}