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/******************************************************************************
This file contains routines that can be bound to a Postgres backend and
called by the backend in the process of processing queries. The calling
format for these routines is dictated by Postgres architecture.
******************************************************************************/
#include "postgres.h"
typedef struct Complex
{
double x;
double y;
} Complex;
/* These prototypes declare the requirements that Postgres places on these
user written functions.
*/
Complex *complex_in(char *str);
char *complex_out(Complex * complex);
Complex *complex_add(Complex * a, Complex * b);
bool complex_abs_lt(Complex * a, Complex * b);
bool complex_abs_le(Complex * a, Complex * b);
bool complex_abs_eq(Complex * a, Complex * b);
bool complex_abs_ge(Complex * a, Complex * b);
bool complex_abs_gt(Complex * a, Complex * b);
int4 complex_abs_cmp(Complex * a, Complex * b);
/*****************************************************************************
* Input/Output functions
*****************************************************************************/
Complex *
complex_in(char *str)
{
double x,
y;
Complex *result;
if (sscanf(str, " ( %lf , %lf )", &x, &y) != 2)
{
elog(ERROR, "complex_in: error in parsing \"%s\"", str);
return NULL;
}
result = (Complex *) palloc(sizeof(Complex));
result->x = x;
result->y = y;
return result;
}
/*
* You might have noticed a slight inconsistency between the following
* declaration and the SQL definition:
* CREATE FUNCTION complex_out(opaque) RETURNS opaque ...
* The reason is that the argument pass into complex_out is really just a
* pointer. POSTGRES thinks all output functions are:
* char *out_func(char *);
*/
char *
complex_out(Complex * complex)
{
char *result;
if (complex == NULL)
return NULL;
result = (char *) palloc(60);
sprintf(result, "(%g,%g)", complex->x, complex->y);
return result;
}
/*****************************************************************************
* New Operators
*****************************************************************************/
Complex *
complex_add(Complex * a, Complex * b)
{
Complex *result;
result = (Complex *) palloc(sizeof(Complex));
result->x = a->x + b->x;
result->y = a->y + b->y;
return result;
}
/*****************************************************************************
* Operator class for defining B-tree index
*****************************************************************************/
#define Mag(c) ((c)->x*(c)->x + (c)->y*(c)->y)
bool
complex_abs_lt(Complex * a, Complex * b)
{
double amag = Mag(a),
bmag = Mag(b);
return amag < bmag;
}
bool
complex_abs_le(Complex * a, Complex * b)
{
double amag = Mag(a),
bmag = Mag(b);
return amag <= bmag;
}
bool
complex_abs_eq(Complex * a, Complex * b)
{
double amag = Mag(a),
bmag = Mag(b);
return amag == bmag;
}
bool
complex_abs_ge(Complex * a, Complex * b)
{
double amag = Mag(a),
bmag = Mag(b);
return amag >= bmag;
}
bool
complex_abs_gt(Complex * a, Complex * b)
{
double amag = Mag(a),
bmag = Mag(b);
return amag > bmag;
}
int4
complex_abs_cmp(Complex * a, Complex * b)
{
double amag = Mag(a),
bmag = Mag(b);
if (amag < bmag)
return -1;
else if (amag > bmag)
return 1;
else
return 0;
}
/*****************************************************************************
* test code
*****************************************************************************/
/*
* You should always test your code separately. Trust me, using POSTGRES to
* debug your C function will be very painful and unproductive. In case of
* POSTGRES crashing, it is impossible to tell whether the bug is in your
* code or POSTGRES's.
*/
void test_main(void);
void
test_main()
{
Complex *a;
Complex *b;
a = complex_in("(4.01, 3.77 )");
printf("a = %s\n", complex_out(a));
b = complex_in("(1.0,2.0)");
printf("b = %s\n", complex_out(b));
printf("a + b = %s\n", complex_out(complex_add(a, b)));
printf("a < b = %d\n", complex_abs_lt(a, b));
printf("a <= b = %d\n", complex_abs_le(a, b));
printf("a = b = %d\n", complex_abs_eq(a, b));
printf("a >= b = %d\n", complex_abs_ge(a, b));
printf("a > b = %d\n", complex_abs_gt(a, b));
}
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