Formula

Description

 

You can create fields that are calculated instead of being entered by the user. These fields are called the formula fields. When you create a formula field, you have to specify the formula expression based on which the value for this field is calculated. You can add, subtract, multiply or divide

Depending on the output of the formula, the value held by a formula field could be numeric values, text values, dates, and durations.

 

The formula evaluation is nothing but expression evaluation and is explained in detail in Expressions. In the below given sample, the field TotalMarks is of type formula.

  
TotalMarks
(
    type  =  formula
    value  =  English  +  Arts
)

 

English and Arts are the fields and they get generated as variables in deluge. But one formula field cannot be used in another formula field.
i.e. The following code is invalid.

 

TotalMarks
(
    type = formula
    value = English + Arts
)
AverageMarks
(
    type = formula
    value = TotalMarks / 2
)

 

Note: Since formula fields are calculated, they do not get displayed in the form when it is rendered. User can choose to view these fields in the form view.

 

Complete Sample

 

application "Student marks database"
{
    page "Enter marks"
    {
        form  Students_Mark_Sheet
        {
            displayname = "Students Mark Sheet"
            Student_Name
            (
                displayname = "Student Name"
                type = text
            )
            English
            (
                type =  number
                decimalplace =  2
            )
            Arts
            (
                type = number
                decimalplace =  2
            )
            TotalMarks
            (
                type = formula
                value = English + Arts
            )
            AverageMarks
            (
                type = formula
                value = (English + Arts) / 2
            ) 
        }
        list "View student marks"
        {
            Students_Mark_Sheet
        }
    }
}

 

Note:

  • All types of form fields except multiple select fields can be used in formulas.
  • The operators/functions that can be used in formulas can be found in the sections Operators and Built-in functions.
  • The formulas will get recalculated when,
    • the formula is modified
    • the values of the fields participating in the formula gets modified (when a record is updated).

 

Also refer FAQ -> Form Fields -> Formula fields.