/*
 *  call-seq:
 *     dvector.asin   ->  a_dvector
 *  
 *  Returns of copy of _dvector_ with entry x replaced by asin(x).
 *     
 *     a = Dvector[ 0.1, -0.2, -0.3, 0.4 ]
 *     a.asin   -> Dvector[ asin(0.1), asin(-0.2), asin(-0.3), asin(0.4) ]
 */ 
VALUE dvector_asin(VALUE ary) {