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
Note: Operators of equal precedence are evaluated from left to right in the expression.
Parentheses can be used to explicitly determine the order of evaluation, overriding the order described above. Each pair of parentheses can contain only one Boolean expression. For example:
not (Salary > 4500 xor LastName = ‘Smith’)
causes the XOR expression to be evaluated before the NOT.
Examples
Some examples of Boolean expressions are shown below:
DeptNum=’Sports’ and Salary > 45000 and LastName = ‘Smith’
Logically true when all three conditional expressions are true; otherwise, logically false.
LastName = ‘Allan’ or Firstname = ‘Allan’
Logically true when either of the conditional expressions is true; otherwise, logically false.
not Salary > 45000
Logically true when the conditional expression is logically false and vice versa.
not ProdCode between 542 and 863
Logically true when the conditional expression is logically false and vice versa.
not LastName in (‘Smith’, ‘Jones’)
Logically true when the conditional expression is logically false and vice versa.
not FirstName like ‘ Sm%’
Logically true when the conditional expression is logically false and vice versa.
Boolean expressions use Boolean operators to compare operands (typically, conditional expressions). When evaluated, Boolean expressions yield a logical result (true or false), depending on the nature of the Boolean operator and the values of the conditional expressions.
The standard rules of precedence for Boolean evaluation are used.
The software ceases to evaluate a Boolean expression as soon as the final result can be correctly predicted. For example, with OR, if the first conditional expression is logically true, then the Boolean expression must be logically true. The software does not bother to evaluate the remaining conditional expressions.
In the expression
LastName = 'Smith' or DeptNum = 'Sports'
if LastName = ‘Smith’ is logically true, then DeptNum = ‘Sports’ is not evaluated.
Note: Taking Boolean evaluation logic into account can be important to the functioning of an application program. For example, if any of the value expressions in the Boolean expression is written in the special assignment format, the assignment is not made if the portion of the Boolean expression containing the assignment is not evaluated.
Boolean Operators
| Operator | Meaning |
| not expr | NOTs the logic expression to the right. If the logic expression is true, the result of the Boolean expression is false; if the logic expression is false, the result of the Boolean expression is true. |
| expr and expr | ANDs two logic expressions (one to the left and one to the right). If both logic expressions are true, the result of the Boolean expression is true; otherwise, the Boolean expression is false. |
| expr or expr | ORs two logic expressions (one to the left and one to the right). If either (or both) of the logic expressions is (are) true, the result of the Boolean expression is true; if both of the logic expressions are false, the Boolean expression is false. |
| expr xor expr | XORs two logic expressions (one to the left and one to the right). If either of the logic expressions is true, the result of the Boolean expression is true; if both of the logic expressions are true or if both are false, the Boolean expression is false. |
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