From: BENI <rajib.chakrabarti@...>
Date: 2007-03-13T19:10:15+09:00
Subject: ta-lib port with swig

ta-lib is a collection of math/statistical function library for price
variability analysis written in C.

There is no port availiable for it in ruby.

Since i badly needed one .. so i started researching on.

I went along the pickaxe book.
since there are about 120 odd functions to port .. I was thinking to
embark upon the SWIG.

I read along the SWIG  docs and ruby mailing list  for hints but
somehow could not zero upon how to kick start.

one of the function header looks like this
=========================
TA_RetCode TA_MA( int          startIdx,
                  int          endIdx,
                  const double inReal[],
                  int          optInTimePeriod,
                  int          optInMAType,
                  int         *outBegIdx,
                  int         *outNbElement,
                  double       outReal[],
                )
==========================

this is called from c in this way

=======================
Lets say you wish to calculate a 30 day moving average using closing
prices. The function call could look as follow:

TA_Real    closePrice[400];
TA_Real    out[400];
TA_Integer outBeg;
TA_Integer outNbElement;

/* ... initialize your closing price here... */

retCode = TA_MA( 0, 399,
&closePrice[0],
30,TA_MAType_SMA,
&outBeg, &outNbElement, &out[0] );

/* The output is displayed here */
for( i=0; i < outNbElement; i++ )
   printf( "Day %d = %f\n", outBeg+i, out[i] );
==================================

given this I was wondering If I would need to write  some typemaps for
SWIG or the typemap.i  inclusion will be sufficient?

Specifically....

 In the C function  above the <const double inReal[]> argument is
passed as &closePrice[0] ... In ruby i won't be able to do that... I
will have to pass in an array containing.... double.. how do i do that
using typemap?

==============

Cheers

Rajib