xsub.c

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#include <grass/gis.h>
#include <grass/raster.h>
#include <grass/calc.h>
 
/****************************************************************
sub(a,b) = a - b
****************************************************************/
 
int f_sub(int argc, const int *argt, void **args)
{
    int i;
 
    if (argc < 2)
        return E_ARG_LO;
    if (argc > 2)
        return E_ARG_HI;
 
    if (argt[1] != argt[0] || argt[2] != argt[0])
        return E_ARG_TYPE;
 
    switch (argt[0]) {
    case CELL_TYPE: {
        CELL *res = args[0];
        CELL *arg1 = args[1];
        CELL *arg2 = args[2];
 
        for (i = 0; i < columns; i++) {
            if (IS_NULL_C(&arg1[i]) || IS_NULL_C(&arg2[i]))
                SET_NULL_C(&res[i]);
            else
                res[i] = arg1[i] - arg2[i];
        }
        return 0;
    }
    case FCELL_TYPE: {
        FCELL *res = args[0];
        FCELL *arg1 = args[1];
        FCELL *arg2 = args[2];
 
        for (i = 0; i < columns; i++) {
            if (IS_NULL_F(&arg1[i]) || IS_NULL_F(&arg2[i]))
                SET_NULL_F(&res[i]);
            else
                res[i] = arg1[i] - arg2[i];
        }
        return 0;
    }
    case DCELL_TYPE: {
        DCELL *res = args[0];
        DCELL *arg1 = args[1];
        DCELL *arg2 = args[2];
 
        for (i = 0; i < columns; i++) {
            if (IS_NULL_D(&arg1[i]) || IS_NULL_D(&arg2[i]))
                SET_NULL_D(&res[i]);
            else
                res[i] = arg1[i] - arg2[i];
        }
        return 0;
    }
    default:
        return E_INV_TYPE;
    }
}