Category: Constructing Expressions

Writing Expressions

Arithmetic operators and parentheses can be combined to create long, complex expressions. Arithmetic expressions are evaluated based on the standard rules of precedence. Parentheses alter the order of evaluation.

Spaces between operands and operators can be used for clarity, but are not required.

For example, Salary * 1.1 and Salary*1.1 are equivalent.

Data Types

Arithmetic expressions yield a numeric result (if possible).

Operands should preferably be of a numeric data type, but character types are converted into an equivalent number as shown in the following example:

” ” (a space) is 0.

“-2″+5 is 3.

“2”*”-4″ is -8.

If a character value cannot be converted to a number (e.g., “abcd”), an error message is returned and the value is treated as 0.

Decimals and Rounding

The result of an arithmetic expression has as many decimal places as are found in the operand with the most decimal places in the expression. If the result is assigned to a field, variable, or form field that has fewer decimal places than the result, the result takes on the number of decimal places in the field, variable, or form field. Results are rounded as required. Rounding occurs only after the entire expression has been evaluated as shown in the following examples:

5/2 is 3

5/2.0 is 2.5

1+1.01 is 2.01

1.01+(5/2) is 3.51

ZIM-X provides a number of built-in functions to perform date and time arithmetic.  If an arithmetic expression subtracts one date from another (i.e., both operands are of data type DATE), the result is a number representing the number of days between the two dates.

Example

Consider the Date Type values: Date1 = 19990923 (23SEP1999) and Date2 = 19980923 (23SEP1998).  We can now apply arithmetic to the dates by simply doing the following:

Date1 – Date2 evaluates to 365. Because the numbers are Date Types, ZIM equates to Date1 to 19990923 and Date2 to 19980923. If the same calculation was performed with INT Data Types the result would be 10,000.

If you add (subtract) a value that is not a date to (from) a date, the result is a date equal to the date operand plus (minus) the number of DAYS indicated by the non-date operand.

Date1 - 100 equates to 19990923 - 100, but evaluates to 19990615 (15Jun1999 - not 19990823)
Date1 + 100 equates to 19990923 + 100, but evaluates to 20000101 (1Jan2000- not 19991023)

Comments

You can covert a Number Type value to do a Date Type value by using $todate().

If you use dates in any other type of operation, the dates are treated as numbers:

Date1/100 equates to 19990923/100, and evaluates to 199909.

See Also

$addyears

$addmonths

$addminutes

$addhours