About Functional Expressions

The software provides a host of built-in functions that process given arguments in a variety of ways. An expression consisting of a function and its arguments (typically, value expressions) is called a functional expression.

Examples of functional expressions are

General Performance

Functions are a special class of operator, but they perform much like arithmetic operators; they take one or more given values, perform an operation using those values, and return a result. The value of the result depends on the function.

The function’s arguments are similar to the arithmetic operands. Like arithmetic operands, the arguments can consist of literals or value expressions, including other functional and arithmetic expressions as shown in the following example:

$absolute(-7)

The functional expression shown above consists of the argument -7 and the function keyword $absolute. The function $absolute returns the absolute (i.e., unsigned) value of its argument (in this case, 7).

Complex Arguments

If the argument is a complex expression, the argument is evaluated before the function is applied. For example, in the expression

$absolute(6-11)

the arithmetic expression 6-11 is evaluated first, yielding $absolute(-5). Then the final result (5) is determined.

Functional expressions can act as arguments to other functions. For example, the expression

$toupper($substring(‘abcdef’,2,3))

evaluates to

$toupper(‘bcd’)

which in turn evaluates to

‘BCD’

Data Type of Arguments and Results

Each function expects arguments of a certain data type; however, the function accepts arguments of any data type and appropriately converts any argument that does not conform to the expected type.

A character literal is any string of characters enclosed in quotation marks as shown in the following example:
‘This is a character string.’
“This is a character string, too.”
For convenience, you can enter character literals without the delimiting quotation marks; however, quotation marks are required in some situations. The rules for using quotation marks are described in Quotation Marks.
Valid and Invalid Literals
The following are examples of valid literals:
‘abc’
Is a character string.
‘ab”C’
Is a character string.
”
Is a null string.
3.14159
Is a number literal.
9
Is a number literal.
‘10.99’
Is a character string.
‘John\’s toy boat’
Is a character string.
‘ABCd_EfG’
Is a character string.
‘1234A’
Is a character string.
The following are examples of invalid literals:
1 23
Spaces are not permitted in number literals.
$10.99
Periods are not permitted in an unquoted character string, and the dollar sign is not permitted in a number literal.
‘John’s toy boat’
‘John’ is a valid character string, but the rest of the line is invalid.

The Purpose of Masking Patterns

Masking patterns are used to format data values in a manner appropriate to the type of information they represent.

For example, in Zim, dates are stored as a special type of numerical value, in which the first four digits represent the year, the next two represent the month and the last two stand for the day.

As such, the date June 28, 2014 is stored numerically as 20140628. This allows for mathematical operations to be performed on dates, but this format is not intuitive for presentation.

By using a masking pattern, such as “DD/MM/YYYY”, this date value will now be presented as the string “28/06/2014”, which is instantly recognized as a date.

The same masking pattern is also used to format the input of data into a date entry field. Instead of typing 20140628, the end-user can type 28062014, because the separator character / is only presented between the year, month and day values, but is not actually part of the date value itself.

The same principle can be applied to separator characters in currency values, postal codes, phone numbers, etc.

Situations in Which Masking Patterns Are Used

Zim offers the possibility of applying data masking patterns in different situations, each with a specific set of fixed and masking characters, as summarized in the table below (follow the links in the first columns for more information):

Masking Characters According to Data Types

The set of available masking characters is different according to the Data Type property (DT) of the entity set field or the entry field.

The following sections describe the available masking characters for each data type:

Alphanumeric Masking

Alphanumeric masking is used to format generic text data. It is particularly useful when data is entered in shortened form but displayed in full form.

In the output value, each question mark is replaced by one character from the current value of the report item, in order from left to right.

When no more characters remain in the value, any remaining question marks become spaces.

Alphanumeric Masking Characters

Examples

Field Mask      MASK      $mask

Leading or trailing spaces are indicated by / in the Output column.

Data Mask

Note:

If the CM (compress status) attribute of a form field is N, the value of the form field is the same as the displayed data. Otherwise, the value of the form field is the same as the input data vlue.

lf the mask pattern is shorter than the field length, then the mask is assumed to contain ? characters in the missing positions (See the last example above).

Non-Digit Masking

Non-digit mask patterns are nearly identical to alphanumeric ones, with the exception that digits (0, 1, …, 9) are not accepted as valid input.

Date Masking

Date masks are composed of three types of character groups, representing the year, month and day, which can be combined in any order.

Between each group there may be an optional fixed separator character, such as /, –, ., or blank space, which appear in the display or output as is.

For date entry fields, the default masking pattern is MM/DD/YY.

Date Masking Characters

Examples

Field Mask      MASK      $mask

Leading or trailing spaces are indicated by / in the Output column.

Data Mask

Numeric Masking

When the data item contains decimals, the decimal point in the mask pattern is aligned with the decimal point in the value, and digit substitutions are made from right to left for the mask characters to the left of the decimal point, and from left to right for the mask characters to the right of the decimal point.

A series of 9s can therefore be used to force the printing of non-significant zeros to the right of the decimal point (in dollar values, for example). A 9 would also be used to force the printing of leading zeros in serial numbers: for example, 009876.

Any report item whose current value is too large to fit in the specified mask pattern (including the sign output, if applicable) causes the overflow characters (asterisks) to be displayed.

• the currency placeholder ($) and sign placeholders: plus (+), minus (–), left and right parentheses (( and )), and the special character strings CR and DB

The currency placeholder inserts the applicable currency symbol into the output value.

Sign placeholders reflect the sign of the number (positive or negative) in the output value. The left parenthesis can be used only on the left-hand side of the mask pattern. The CR, DB and left and right parenthesis can be used only on the right-hand side of the mask pattern. The plus and minus signs can be used on either side of the mask pattern.

The plus and minus signs, left parenthesis, and the dollar sign can be used as float characters. A single plus, minus, dollar sign, or left parenthesis can also “float” ahead of a series of other floating characters.

• fixed text characters

Typically, in the output value, fixed text characters (e.g., commas) appear as is, provided that there are digits remaining to be substituted into the mask or that the mask character 9 forces the output of zeros.

Numeric Masking Characters

Examples

Field Mask      MASK      $mask

Leading or trailing spaces are indicated by / in the Output column.

Data Mask

The software maintains a series of system variables that represent either fixed values ($ZimOS) or values that fluctuate dynamically with the current status of the software ($InTransaction) or of application objects (ThisWindow.WindowTag).

System variables resemble global variables in nature. The software automatically sets or resets the values of system variables to reflect the status of the software and the current application. In some cases, an application program can also reset them.

A system variable name can be used as an atomic expression denoting the value currently held in the memory location associated with the variable. A system variable name can be used almost anywhere that a literal can be used.

Available System Variables

System variables are categorized into those that supply information about windows, those that supply information about menus, those that supply information about forms, and those that supply general information. Some system variables are “binary” in nature in that they evaluate only to ‘1’ ($True) or ‘0’ ($False), while others may be set to a variety of values.

General-use System Variables with “Permanent” Values

Given a particular version of the software, the following system variables have the same value at all times during an application session:

General-use System Variables with Values Derived from the Operating System

The software sets the values of the following system variables based on current values obtained from the operating system:

System Variables Periodically Set/Reset by the Software or the Application System

The values of these variables are set and reset depending on conditions encountered during execution of the application. An application program can assign a value to any of these variables at any time; however, the assigned value can be overwritten as conditions subsequently change during the application session.

Last Callback Event

Event is a data structure that provides information about the application environment the time of the most recent callback even. Each variable in the structure provides one item of information. The values of these variables are reset each time a callback event returns control to the application program. An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that a callback event occurs.

Text Cursor Positioning

Error Status

Other Status Conditions

External Programs

Security

System Variables Concerned with Windows

Last Event in the Current Window

ThisWindow is a data structure that provides information about the state of the application environment and of the current window at the time of the last event in that window. Each variable in the structure provides one item of information. The values of these variables are reset each time a window becomes the current window. An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that another window becomes the current window.

Miscellaneous

System Variables Concerned with Menus

Last Event in the Current Menu

ThisMenu is a data structure that provides information about the state of the software environment and of the current menu at the time of the last event in that menu. Each variable in the structure provides one item of information. The values of these variables are reset each time that FORM or MENU INPUT terminates. An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that FORM or MENU INPUT terminates.

System Variables Concerned with Forms

Last Event in the Current Form/Display

ThisForm is a data structure that provides information about the state of the current form/display at the time of the last event in the current window. Each variable in the structure provides one item of information. The values of these variables are reset each time that FROM or MENU INPUT terminates, An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that FORM or MENU INPUT terminates.

A character literal is any string of characters enclosed in quotation marks as shown in the following example:

'This is a character string.'
"This is a character string, too."

For convenience, you can enter character literals without the delimiting quotation marks; however, quotation marks are required in some situations. The rules for using quotation marks are described in Quotation Marks.

Valid and Invalid Literals

The following are examples of valid literals:

The following are examples of invalid literals:

If you need a place a character not normally available from the keyboard into a character literal, use the backslash to create the hex code for that character as shown in the following example:

‘This string has an ASCII escape generated by hex 1B (1B)’

The two characters immediately following a quoted backslash are treated as hex code provided they are either digits from 0 to 9 or letters from A (a) to F (f).

Any character string containing a hex code must be enclosed in quotation marks.

Note: The escape function of the backslash inside quoted character strings can be switched off with a SET ESCAPECHAR command.

Example

Character literals that include hex codes can be useful for sending control codes to printers and terminals. For example, if the ASCII codes SI (hex 0F) and DC2 (hex 12) are used, respectively, to select and cancel condensed printing on your particular printer, use the following sequence of statements to print a report in the condensed mode:

set output printer   % switch serial output to printer
output ‘F’;        % switch condensed print on
…. commands to generate report ….
output ’12’         % switch condensed print off
set output terminal  % switch output back to terminal

Certain characters, such as quotation marks and the backslash, have special functions in the software. If you need to use one of these metacharacters as a literal character in a string, you must “escape” the special function by inserting a backslash ( – Escape) preceding the metacharacter as shown in the following example:

‘This is a quotation mark (‘).’
‘This is a backslash (\).’

Any character string containing a metacharacter used as a literal must be enclosed in quotation marks.

A null string is a character string of zero length. Unlike the $Null property that indicates that the value is unknown or unassigned, the null string is a known value.

For example, if you have two variables, x and y, both of which are null strings, then the expression

x = ” and y <> ‘abc’

is logically true.

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

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.