cmath

cmath is a collection of math functions defined in the ISO C programming language. All functions in <math.h>, except for long double versions (sinl(x), expl(x), etc.), are included with the prefix c_. For example, log10(x) can be called by:

SELECT c_log10(100);

c_log10(x), unlike the PostgreSQL native function log(x), does not raise error when x < 0. Instead, c_log10(x) returns NaN or -Infinity in such cases.

Another example:

SELECT c_exp(1e100);

c_exp(x), unlike the PostgreSQL native function exp(x), does not raise error when the return value is overflowing. Instead, c_exp(x) returns +Infinity in such cases.

Single precision versions of functions are also available:

SELECT c_sinf(0.1), c_cosf(0.1);

Rather newly specified functions are available:

SELECT c_erf(1), c_tgamma(5), c_nextafter(0, 'infinity');

If a function has output parameters, a tuple is returned:

SELECT * FROM c_remquo(13, 5);
/* ret_value | quo
  -----------+-----
          -2 |   3
*/

Install

PostgreSQL must be installed first.

Then

$ make && make install

will install libraries into postgres's library directory. To use it, you have to tell the postgres server to load it:

$ psql -U {super user}
sql> CREATE EXTENSION cmath;
sql> \q

Source code maintenance

The source files are generated automatically by generate_pg_cmath.py. Do not modify src/pg_cmath.c and sql/cmath.sql.in directly.