HP 3000 Manuals

HP ALLBASE/4GL Developer Reference Manual Vol. 1

Calculated Items Screen 

This screen allows you to define a calculated item.  A calculated item is
a variable that contains the result of an algebraic expression or a
function that is evaluated whenever the item is referenced.  Calculated
items exist in two forms, the simple form and the extended form.  HP
ALLBASE/4GL implements both forms of calculated item by executing a
function when the item is referenced.  The function assigns a value to
the calculated item.

In the simple form, you specify the expression to be evaluated as a
single algebraic equation using the CALC logic command.  In the extended
form, rather than specify an algebraic equation, you use a function with
the same name as the calculated item.  This function may perform any
processing that is normally permitted within a function.  The value of
the calculated item must be set explicitly within the function.  To
specify a calculated item in this form, you must first define the name
and attributes of the calculated item using this screen, and then use the
function details screen in the logic menu to define the details of the
function.  Chapter 11 describes HP ALLBASE/4GL functions.

Screen Image 


            

Field Descriptions 

Item Name   Enter the name of the calculated item (up to 16 characters).
When you enter a new calculated item name, HP ALLBASE/4GL automatically
creates a function with the same name.

HP ALLBASE/4GL displays an error message if you enter a name which is
already in use for a function.

Length   Enter the maximum length in characters of the value that can be
assigned to the calculated item by the assigning function.

Edit Code   Enter a code defining the type of data that the calculated
item may contain.  The following table lists the available edit codes and
their meanings.

  Code   Meaning 

   X     Any printable character.

   A     Alphabetic characters only (A to z, extended characters, or
         space).

   U     Forced uppercase.  Same as X edit code, but shifts all lowercase
         alphabetic characters to uppercase.

   K     Alphanumeric characters only (A to z, 0 to 9, extended
         characters, and underscore).

   N     Unsigned number (0 to 9, a period ".", or a comma ",").

   S     Signed number.  Same as N edit code, but may include + or -.

   Q     Question.  Y, y, N, or n only.  Any characters beyond the first
         character in the field are ignored.

   D     Date field.  Must be eight characters long.  The date may be
         either MM/DD/YY or DD/MM/YY (depending on the system-wide date
         format) where MM, DD, and YY represent the month, day, and year
         respectively.

   T     Date field, defaulting to the current date.

Number of Decimal Places   Enter the maximum number of decimal places for
the contents of the calculated item if the item is numeric (edit code N
or S).

Pad Character   Enter a single character used to initialize the
calculated item.  HP ALLBASE/4GL sets every character of the item to the
value of the pad character before calling the assigning function.

CALC   The value of a calculated item is assigned by a function HP
ALLBASE/4GL creates for this purpose.  The function may be either a
simple function or an extended function.

A simple function is one that contains only a single CALC command.  To
create a simple function, enter the details of the CALC command in this
area of the screen.  You don't need to use the command name CALC as part
of this command expression.  HP ALLBASE/4GL assumes the entry in this
field is a CALC command, and displays the word CALC in a display only
field the left of the command field.  Refer to chapter 12 for details of
the CALC command.

An extended function either has more than one step, or consists of a
single step that is not a CALC command.  To define a calculated item
using an extended function, leave the CALC field blank.  You can then use
the function detail screen in the logic menu to define the extended
function.  Note that HP ALLBASE/4GL automatically creates a function
header using the name of the calculated item as the function name, and
the description fields from this screen.  Refer to chapter 11 for details
of function header and function details screens.

The assigning function or a function called from the assigning function
may use the calculated item.  Under these circumstances, the value in the
calculated item is its existing value.  The calculated item is not
re-evaluated if it is used in the assigning function.

Description   Documentation fields.  Enter a description of the
calculated item for documentation purposes.  HP ALLBASE/4GL automatically
updates the date and time fields to show the date and time of the last
modification.

HP ALLBASE/4GL uses the description fields and the calculated item name
to create the function header for the assigning function.

Function Keys 

f1       Variable  Cancels the current screen and displays the variables
        screen.

f2       Function Details  Cancels the current screen and displays the
        function details screen.

f3       Numeric Constant  Cancels the current screen and displays the
        numeric constants screen.

f4       AlphaNum Constant  Cancels the current screen and then displays
        the alphanumeric constants screen.

Additional Information 

You cannot create a calculated item with the same name as a function that
already exists.

Values can only be assigned to a calculated item from within a function
of the same name as the calculated item.

Generating Calculated Items.     

When you press the  Commit Data  function key, HP ALLBASE/4GL generates
the assigning function automatically.  HP ALLBASE/4GL displays an error
message if the function generate fails.

Using Calculated Items.     

In general, you can use calculated items in the same way as you would use
HP ALLBASE/4GL variables, provided you don't move data into the
calculated item.  If you do try to move data into a calculated item, the
application aborts.

Only the assigning function can move a value into a calculated item.

MPE/iX 5.0 Documentation