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Binary arithmetic operators

There are six binary arithmetic operators:

symbol	name	example	left operand	right operand	result
+	addition	a + b	summand	summand	sum
-	subtraction	a - b	minuend	subtrahend	difference
*	multiplication	a * b	factor	factor	product
/	division	a / b	dividend	divisor	quotinent
**	exponentiation	a ** b	base	exponent	power
MOD	modulus	a MOD b	dividend	divisor	integer remainder

Binary arithmetic operators can be used in numeric and time expressions with these restrictions:

+, -, *, and / can be used in all numeric and some time expressions,
** and MOD cannot be used in time expressions

	+	-	*	/	**	MOD
Numeric
DATE
DATETIME
INTERVAL

4gl performs calculations with binary arithmetic operators on numeric data types after automatically converting both operands to DECIMAL:

MOD operands are first converted to INTEGER.
If an arithmetic expression has several operators of the same precedence, 4gl processes them from left to right.
If any operand of an arithmetic expression is a NULL value, the expression returns NULL.
The right-hand integer operand of the exponentiation operator (**) cannot be negative.
If both operands of the division operator (/) have INTEGER, BIGINT, or SMALLINT data types, 4gl discards any fractional portion of the quotient.
If the right-hand operand of the division operator is equal to zero, you will get a runtime error.

When you use time operands in expressions with arithmetic operators, you must use DATETIME or INTERVAL literals that include an appropriate qualifier:

LET time_difference = DATETIME (2005-01-01 01:01:01.001) YEAR TO FRACTION - DATETIME (1995-01-01 01:01:01.001) YEAR TO FRACTION

If you put your date-and-time value or time interval as a quoted string, you will get a compilation error:

LET time_difference = "2005-01-01 01:01:01.001" - "1995-01-01 01:01:01.001"

This table shows the precedence of the binary arithmetic operators and data types for their operands and returned values:

expression	left operand	right operand	returned value	precedence
a + b	numeric	numeric	numeric	10
	INT or SMALLINT	DATE	DATE
	DATE	INT or SMALLINT	DATE
	DATE or DATETIME	INTERVAL	DATETIME
	INTERVAL	DATE or DATETIME	DATETIME
	INTERVAL	INTERVAL	INTERVAL
a - b	numeric	numeric	numeric
	INT or SMALLINT	DATE	DATE
	DATE	INT or SMALLINT	DATE
	DATE or DATETIME	INTERVAL	DATETIME
	DATE or DATETIME	DATETIME	INTERVAL
	DATETIME	DATE	INTERVAL
	INTERVAL	INTERVAL	INTERVAL
	DATE	DATE	INT
a * b	numeric or INTERVAL	numeric	same as b	11
a / b	numeric or INTERVAL	numeric	same as a	11
a ** b	numeric	INT or SMALLINT	same as b	12
a MOD b	INT or SMALLINT	INT or SMALLINT	same as b	12

Time operands not listed here produce either errors or meaningless results.