s17aef

Purpose

Synopsis

[fun_value,ifail] = s17aef(x<,ifail>)

Description

 
 This routine evaluates an approximation to the Bessel Function of
 the first kind J (x).
                 0   
 
 Note: J (-x)=J (x), so the approximation need only consider x>=0.
        0      0                                                 
 
 For very large x, it becomes impossible to provide results with 
 any reasonable accuracy, hence the routine fails. Such arguments 
 contain insufficient information to determine the phase of 
                                               ________ 
                                              /    2    
 oscillation of J (x); only the amplitude,   /  -------, can be 
                 0                         \/   (pi)|x| 
 determined and this is returned on soft failure. The range for 
 which this occurs is roughly related to the machine precision;  
 the routine will fail if |x|>~1/machine precision
 

Parameters

s17aef

Required Input Arguments:

x                                     real

Optional Input Arguments:                       <Default>

ifail                                 integer  -1

Output Arguments:

ifail                                 integer