TDL – Prefixes and Symbols

There are a few symbols as TDL components  that are used for specific tasks. Prefixes/ some symbols act as access specifiers, which means they are primarily used to get the value of a method, variable, field, formula, and so on. Modifiers, for example, are applied in normal situations.

Access Specifiers/Symbol Prefixes

Mentioned below are Access Specifiers/Symbol Prefixes

General Symbols

The Usage of @ and @@

Formula

Large complex calculations in TDL can be deconstructed into smaller basic equations or expressions written as a Formula. The symbol prefixes @ and @@ can be used to retrieve the values computed using these formulas.

Formula Naming Conventions

• Insensitive case
• The use of only alphanumeric characters is permitted.
• At Definition time, space is insensitive. However, spaces are not permitted during deployment or use of the same.

Formula classifications

• Formula for local
• Formula for Globe

Use @ to define a local formula

Any Interface Definition can define and get a Local Formula. The local formula’s scope is within the present definition. When a formula is definition-specific and not needed by any other definition, it is generally local formula.

The Symbol Prefix @ can be used to get the Local Formula value.

Example

Using the Local Formula this code can also be written, as:

Use @@ to define a Global Formula

A global formula is one that is available anywhere in the world after being defined once. In other words, all Definitions have access to the Global Formula value. When a formula is needed in multiple places, it is defined as a global formula. The Symbol Prefix @@ can be used to get the Global Formula value. A System Formula is another term for a Global Formula.

Example

All of the Fields in this example have identical widths. If the field width needs to be changed, only the [System: Formula] Definition Section needs to be changed. Using the Global Formula AmtWidth, this adjustment will be implemented to all Fields.

# and ## Usage

# (Symbol Prefix) can be used in TDL for:

• Using # to refer a field
• Using # to modify the existing definitions

Using # to refer a field

To extract the value from another Field, use # Symbol Prefix.

The Field value ‘HW’ is placed to the Field ‘HW1′ in this example. In other terms, #HW is used to set the Field HW1 to “Hello World.”

Use # for Modifying existing Definitions

Existing definitions can also be modified using # Symbol Prefix. The definition’s attributes can be altered. For instance, insert a new Field in the ‘Line‘ definition.

Example

In this example, the existing ‘Gateway of Tally’ (default Menu) has been modified to include the ‘Hello World’ Item and the Menu Title has been modified to “Tally Gateway“.

Accessing value from a Variable using ##

A Variable is a named data container that can be changed as needed. Variables in TDL are divided into two categories: local and global variables. Within a single Report, local variables preserve their value. On contrary, Global variables depending on the ‘Variable’ Definition, preserve their values during the session or permanently.

The symbol prefix ## can be used to access the Variable value. ## can be used to retrieve both local and global variables. The local variable is evaluated first. If the Local Variable is not identified, the value of the Global Variable is assumed.

Example

$ and $$ Usage

Use $ For Accessing a Method

A Method or UDF can be used to extract any data from an Object. The $ Prefix is utilized to deploy any Object value from Method or UDF, where the ‘Method’ and ‘Object’ terms are TDL-specific. In the parts below, we’ll go through this in further detail.

Context Fall Through for $

• Verify if it’s an Internal method or a UDF within the current object.
• User-Defined Method
• The formula for the System
• Repeat the above steps after changing the context as the parent object.

Example

The value of the linked object’s method “Name” is displayed in this code snippet.

Use $$ For Calling an Internal Function

Functions are in-built in TDL and can be used by TDL programmers. A function can take zero or even more arguments and perform a task on them before returning a value. Spaces and special characters with the exception of bracket () are not permitted when giving arguments to functions, to return the expression result as a function parameter.

Example

Use ;, ;; and /**/ for commenting a Code

Commenting improves the readability. Symbol prefixes like-;, ;; and /* */ can be used to give comments in TDL. Part line commenting is done with Symbol Prefix;, single line commenting is done with ;; and multi-line commenting is done with /* */. The TDL Interpreter will treat all lines enclosed in /* and */ as comments and ignore them.

For single-line comments, a single semi-colon (;) is appropriate as a comment, although it is advised to use a Double Semi-Colon (;;) as per a standard coding approach.

Example

Line Continuation Character (+)

The Line Continuation Character (+) is used to break up a long line into several smaller lines. The programmer can now see the complete line without having to scroll to the left or right. This can also make it easier to comprehend and debug the code.

Example

Exposing Methods and Creating Procedures (_)

Methods are exposed to ODBC using the Symbol Prefix (_). When a Collection Name is prefixed with _, it becomes a procedure that may be referenced externally by giving the parameter as a Variable.

Example

Example

Optional Definitions (!)

Optional definitions are defined using the Symbol Prefix !. Attributes   ‘Switch’ and ‘Option’ are used to deliver a conditional outcome in TDL via various definitions such as Menu, Form, Part, Line, Field, Collection, Button, Key, Import File, and Import Object. They cannot, however, be combined with Report, Color, Style, Variable, System Formula, System Variable, System UDF, Border, or Object definitions.

Only if the Logical Condition is fulfilled, the original definition attributes are overruled by the optional definition attributes. To put it another way, if the Logical Condition returns TRUE, the optional definition’s attributes become part of the original definition; otherwise, they are dismissed, leaving the original definition unchanged.

Syntax

Option : <Optional Definition> : <Logical Condition>

Switch : Label : <Optional Definition> : <Logical Condition>

Switch and Option differ in a way that ‘Switch‘ statements bear the same label are run until a satisfying condition is obtained. On the other hand, ‘Option‘ runs all of the Option statements that match the provided conditions in order. Switch statements bearing distinct labels are identical to Option statements, in that all Switch statements will all be performed as the conditions provided.

Example – Option

The condition indicated in both options will be verified in this code snippet and the options meeting the specified condition will be performed. In this circumstance, it’s possible that more than one criteria are met and the action is carried out.

Example – Switch

The conditions mentioned in the switch statements will be verified one by one in this code snippet. In contrast to ‘Option,’ just the first statement fulfilling the specified condition is performed, and all other statements gathered under the label ‘Case 1′ are not implemented further. If desired, a behavior similar to that of ‘Option’ can be implemented by defining different labels.

Conclusion:

The different special symbols used in TDL include Access Specifiers and General symbols. The @ and @@ Access Specifiers are used to access the local and global formulas values, respectively. # can be used to refer to a field or to make changes to an existing definition. The ## symbol is used to access the Local or Global variable values. Accessing a method or UDF $$ is used and for calling a function $$ is used. For any Tally on Cloud service-related details visit Tallystack.in.