Arithmetic Functions and Operators

Compared with the original openGauss, Dolphin modifies the time/date function as follows:

The DIV, MOD, XOR, and ^ operators are added.
The truncate, rand, crc32, conv, float8_bool, oct, and float4_bool functions are added.
Implement the atan function to support the usage of atan(y, x).

DIV

Description: Division (rounded)

Example:

openGauss=# SELECT 8 DIV 3 AS RESULT;
 result 
--------
      2
(1 row)

MOD

Description: Model (to obtain the remainder)

Example:

openGauss=# SELECT 4 MOD 3 AS RESULT;
 result 
--------
      1
(1 row)

XOR

Description: Binary XOR

Example:

openGauss=# SELECT 4 XOR 3 AS RESULT;
 result 
--------
      0
(1 row)

truncate(v numeric, s int)
Description: Truncates a number with s digits after the decimal point. It is equivalent to trunc.
Return type: numeric
Example:
```
openGauss=# SELECT truncate(42.4382, 2);
 truncate
----------
    42.43
(1 row)
```
rand()
Description: Random number between 0.0 and 1.0 It is equivalent to random.
Return type: double precision
Example:
```
openGauss=# SELECT rand();
       rand
-------------------
 0.254671605769545
(1 row)
```
crc32(string)
Description: Calculates the crc32 value of string.
Return type: int
Example:
```
openGauss=# SELECT crc32('abc');
   crc32
-----------
 891568578
(1 row)
```
conv(input in, current_base int, new_base int)
Description: Converts a number or string from one number base system to another. The value of in can be a number or a character string.
Return type: text
Example:
```
openGauss=# SELECT conv(20, 10, 2);
 conv
-------
 10100
(1 row)

openGauss=# SELECT conv('8D', 16, 10);
 conv
------
 141
(1 row)
```
^
Description: Implements bitwise XOR between two integers.
Return type: INT
Example:
```
openGauss=# SELECT 1^1;
?column?
----------
       0
(1 row)
```
Description: After set b_compatibility_mode is set to 1, the float data can be bitwise XOR or XOR after rounded off.
Return type: DOUBLE
Example:
```
openGauss=# select 0.5678::float^1.1234::float;
 ?column? 
----------
        0
(1 row)
```
float8_bool(float)
Description: Returns a Boolean value based on the value of a floating point number. If the value is 0, false is returned. Otherwise, true is returned.
Return type: Boolean
Example:
```
openGauss=# select float8_bool(0.1);
 float8_bool 
-------------
 t
(1 row)
```
```
openGauss=# select float8_bool(0.0);
 float8_bool 
-------------
 f
(1 row)
```
oct(input N)
Description: Converts a number or string from a decimal number to an octal number.
Return type: text
Example:
```
openGauss=# SELECT OCT(10);
 oct 
-----
12
(1 row)

openGauss=# SELECT OCT('10');
 oct 
-----
12
(1 row)
```
float4_bool(float)
Description: Returns a Boolean value based on the value of a floating point number. If the value is 0, false is returned. Otherwise, true is returned.
Return type: Boolean
Example:
```
openGauss=# select float4_bool(0.1);
 float4_bool 
-------------
 t
(1 row)
```
```
openGauss=# select float4_bool(0.0);
 float4_bool 
-------------
 f
(1 row)
```

atan(y, x)

Description: Arc tangent of y/x.

Return type: double precision

Example:

openGauss=# SELECT atan(2, 1);
      atan
------------------
 1.10714871779409
(1 row)