_CP_convert is equivalent to the convert string1 to string2 in result BASIC statement.
int _CP_convert(CPSTR** result, CPSTR* string1, CPSTR* string2)
This function returns -1 if an error occurs. The error code is contained in _CP_errno.
/* Prints "bbc". */
CPSTR * s = _CP_mkstr("a");
CPSTR * t = _CP_mkstr("b");
CPSTR * u = _CP_mkstr("abc");
_CP_unix_env();
_CP_convert(&u,s,t);
_CP_TERM(u);
printf("%s\n",_CP_SADDR(u));