This is to go with the hypot() patch I posted the other day.
As other code, such as found in adt/float.c and adt/numeric.c, simply
assumes that isnan() exists, despite it being a C99 function, I have
assumed the same.
The below code should be placed into a file called src/port/hypot.c.
Unfortunately I do not know how to drive configure and all the other
associated build magics. Could some kind soul please implemented that
portion. (Or shove me in the right direction)
#include <math.h>
#include "c.h"
#include "utils/builtins.h"
/** Find the hypotenuse. Firstly x and y are swapped, if required, to make* x the larger number. The traditional
formulaeof x^2+y^2 is rearranged* to bring x outside the sqrt. This allows computation of the hypotenuse* for much
largermagnitudes than otherwise normally possible.** sqrt( x^2 + y^2 ) = sqrt( x^2( 1 + y^2/x^2) )* =
x* sqrt( 1 + y^2/x^2 )* = x * sqrt( 1 + y/x * y/x )*/
double hypot( double x, double y )
{ double yx;
if( isinf(x) || isinf(y) ) return get_float8_infinity();
if( isnan(x) || isnan(y) ) return get_float8_nan();
x = fabs(x); y = fabs(y); if (x < y) { double temp = x; x = y; y = temp; } if (x == 0.0)
return 0.0; else { yx = y/x; return x*sqrt(1.0+yx*yx); }
}
