[GENERAL] Functions in postgres

[Victor Manuel Jaquez Leal]

Hi!

I know that with \df you can see the functions available in postgres, but
there must be others not documented just like getpgusername().

My question is if are there a more complete list of postgres'
functions.  To be more specific I'm looking for a crypt function.

BTW

How do I implement a function in C that returns a varchar... 

create function pgcrypt(opaqe) returns varchar....???

char *pgcrypt(char *text) ????