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Language Reference ‐ Identifiers

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Andreas AFENTAKIS edited this page Oct 20, 2025 · 9 revisions

Language Reference - Identifiers

Naming Conventions & Rules

Identifiers are names used within FBasic to uniquely denote program elements such as statements, variables, arrays, collections, and defined functions. This section outlines the specific rules governing the construction and interpretation of these names by the interpreter.

General Rules

All identifiers in FBasic must adhere to the following basic rules:

  • They must begin with a letter (A-Z or a-z).
  • They must be composed exclusively of alphabetic characters (letters) and digits (0-9).
  • No other characters are permitted, including spaces, underscores (_), hyphens (-), or special symbols.

Statement Names

Statement names refer to the keywords that define an action or control flow (e.g., PRINT, PUSH, GOTO).

Rule Specification
Allowed Characters Letters and Digits. Must start with a letter.
Word Structure Must be a single, contiguous word (no spaces).
Case Sensitivity Case-Insensitive. The interpreter treats PRINT, print, and Print as the same statement.

Variable, Array, and Collection Names

These names are used for storing and referencing data. They represent user-defined entities.

Rule Specification
Allowed Characters Letters and Digits. Must start with a letter.
Word Structure Must be a single word.
Case Sensitivity Case-Sensitive. The names MyVar and myvar are treated as two distinct, separate identifiers.

Function Names

Function names follow the same naming conventions and case sensitivity rules as variables, arrays, and collections.

Rule Specification
Allowed Characters Letters and Digits. Must start with a letter.
Word Structure Must be a single word.
Case Sensitivity Case-Sensitive. For example, stackcnt() and StackCnt() would refer to different functions if both were defined.

Examples

The table below illustrates valid and invalid identifiers based on the rules for case-sensitive elements (Variables/Functions).

Identifier Valid? Reason / Status
Total1 Valid Starts with a letter, contains only letters and digits.
CustName Valid Contains only letters.
1stVar Invalid Cannot start with a digit.
Array_X Invalid Contains an illegal character (underscore _).
POPTEMP Valid Valid format, but if it clashes with a statement name, a conflict may arise depending on context.
PopTemp Valid If poptemp is a variable, PopTemp is a different variable due to case-sensitivity.
Final Price Invalid Contains a space (must be one word).

How to use

Once an entity (Variable, Collection, or Array) is declared or created in FBasic, it can be referenced to either read its current value or set/update its value. This section details the syntax used for these read and write (assign) operations. The fundamental syntax for manipulating the value of a non-statement entity is through the assignment statement, usually involving the LET keyword (or implicit assignment).

Setting a Value (Assign Operation)

The syntax to store a new value into an entity is:

[LET] entityName = valueOrExpression
Element Description
[LET] The optional assignment keyword.
entityName The identifier of the Variable, Collection, or Array element being set.
= The assignment operator.
valueOrExpression A literal value, another entity's name, or the result of a mathematical or string expression.

Note: The implicit assignment is supported but its a nice practice to avoid it and specify the LET statement

Reading a Value (Read Operation)

To retrieve a value, the entity's identifier is used as part of an expression:

PRINT entityName
LET anotherVar = entityName

Variables

A simple variable holds a single value (numeric or string) and is referenced solely by its unique identifier.

Operation Syntax Example
Set Value variableName = value TotalSales = 1500.25
Read Value expression LET Margin = TotalSales * 0.1
Print Value PRINT variableName PRINT TotalSales

Collections

Got it. I will remove the section on Collections (Stack) from the previous reference and incorporate the new "Square Bracket Reference" rules for arrays and collections based on your notes. I'll also clarify the default index access.

Here is the revised reference page, focusing only on Variables and Array/Collection referencing:

Language Reference - Referencing Entities

Purpose

Once an entity (Variable, Array, or Collection) is declared or created in FAST.FBasic, it can be referenced to either read its current value or set/update its value. This section details the syntax used for these read and assisgn operations, including standard (parentheses) and specialized (square bracket) access.

How to Use

The fundamental syntax for manipulating the value of a non-statement entity is through the assignment statement, usually involving the LET keyword (or implicit assignment).

Setting a Value (Assign Operation)

The syntax to store a new value into an entity is:

[LET] entityReference = valueOrExpression
Element Description
[LET] The optional assignment keyword.
entityReference The identifier of the Variable, Array element, or Collection member being set (e.g., A, Price(1), [col.column]).
= The assignment operator.
valueOrExpression A literal value, another entity's name, or the result of a mathematical or string expression.

Reading a Value (Read Operation)

To retrieve a value, the entity's reference is used as part of an expression:

PRINT entityReference
LET anotherVar = entityReference

Variables

A simple variable holds a single value (numeric or string) and is referenced solely by its unique identifier.

Operation Syntax Example
Set Value variableName = value TotalSales = 1500.25
Read Value expression LET Margin = TotalSales * 0.1
Print Value PRINT variableName PRINT TotalSales

Arrays (Parentheses Reference)

Arrays hold multiple values of the same type, accessed using a numeric index enclosed in parentheses (). Array indexes typically start at 1 (one). This is the standard BASIC array access method.

Operation Syntax Description Example
Set Value arrayName(index) = value Assigns value to the element at index. Price(2) = 19.99
Read Value arrayName(index) Retrieves the value at index. LET Sum = Price(1) + Price(2)

Square Bracket Reference [] (Advanced Access)

The Square Bracket Reference provides a specialized syntax for accessing complex data structures, specifically columns within collections (tables) and arrays. Brackets may be present or omitted, depending on the context.

Syntax Applies to Description
[col.Item] Static Collections (SDIM) References the value of the current item in the static collection.
[col.column] Collections / Arrays References the value of a column in the collection or array. column can be a column name or a numeric index.
[arr.column(index)] Arrays References the value of a specific column of an array at the specified index. This combines column naming with array indexing.

Examples

REM Example 1: Variables and Standard Array Access
LET A = 10
DIM Price(10)

Price(1) = 9.99
LET Sum = Price(1) + A

PRINT "Total="; Sum
' Output: Total=19.99

REM Example 2: Square Bracket Collection/Column Access
REM Assume a Collection 'ClientData' with a column 'FirstName'
LET Name = [ClientData.FirstName]
PRINT Name

REM Example 3: Square Bracket Array Column Access
REM Assume an Array 'Trades' with a column 'Quantity'
Trades(5) = 100 
' Standard array write (index 5) - assuming 'Quantity' is the default column

LET Qty = [Trades.Quantity(5)]
PRINT "Quantity at index 5: "; Qty
' Output: Quantity at index 5: 100

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