xexp.c

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#include <math.h>
 
#include <grass/gis.h>
#include <grass/raster.h>
#include <grass/calc.h>
 
/**********************************************************************
exp(x)   computes e raised to power x
exp(x,y) computes x raised to power y
 
  if floating point exception occurs during the evaluation of exp(x)
  or exp(x,y) the result is NULL
**********************************************************************/
 
int f_exp(int argc, const int *argt, void **args)
{
    DCELL *res = args[0];
    DCELL *arg1 = args[1];
    DCELL *arg2;
    int i;
 
    if (argc < 1)
        return E_ARG_LO;
    if (argc > 2)
        return E_ARG_HI;
 
    if (argt[0] != DCELL_TYPE)
        return E_RES_TYPE;
 
    if (argt[1] != DCELL_TYPE)
        return E_ARG_TYPE;
 
    arg2 = (argc > 1) ? args[2] : NULL;
 
    for (i = 0; i < columns; i++)
        if (IS_NULL_D(&arg1[i]))
            SET_NULL_D(&res[i]);
        else if (argc > 1 && IS_NULL_D(&arg2[i]))
            SET_NULL_D(&res[i]);
        else if (argc > 1 && arg1[i] < 0 && arg2[i] != ceil(arg2[i]))
            SET_NULL_D(&res[i]);
        else {
            floating_point_exception = 0;
            res[i] = (argc > 1) ? pow(arg1[i], arg2[i]) : exp(arg1[i]);
            if (floating_point_exception)
                SET_NULL_D(&res[i]);
        }
 
    return 0;
}