Interpreter Project

This GitHub repository represents the culmination of several distinct projects undertaken throughout the FALL 2022 semester to develop a comprehensive interpreter for a simple programming language.

Program Execution

Valid Execution of the program necessitates the appropriate header and footer in the file, indicating the program's start and end.

Valid Program:

PROGRAM <PROGRAM-NAME>
    <insert-code>
END PROGRAM

Variables

Variables can be declared without needing to be immediately defined.

Valid Datatypes:

• INT (Integers)
• FLOAT (Floating-Point Numbers)
• BOOL (Boolean)

Variable Declaration:

• Variable names are valid if they are alphanumeric, and can include an underscore (_) or an asperand (@). The variable name must start with either a letter or an underscore and can be followed by zero or more letters, digits, underscores, or asperands.
• Using a variable in an expression before assigning a value to it is invalid.

Valid Variable Declaration:

<datatype> <variable-name>;
<variable-name> = <value>;

Comments

A comment is defined by all the characters following the sequence of characters “/*” as the starting delimiters to the closing delimiters “*/”.

• Comments can span multiple lines.

Mathematical Operators

Valid Mathematical Operators:

• Addition (+)
• Subtraction (-)
• Multiplication (*)
• Division (/)

Unary Operators:

• Positive (+)
• Negative (-)
• Not (!) [only for boolean variables/expressions]

Conditionals and Control flow

Valid Logical Operators include:

• And (&&)
• Or (||)
• Equality (==)
• Greater Than (>)
• Less Than (<)

All logical operators and conditional expressions can be used inside and outside control flow statements including variable declarations.

• Based on their nature, they will only return true or false.

Valid Control Flow:

The "IF" statement is a control flow statement used to conditionally execute a block of code. It allows the program to execute different sets of code based on a specified condition.

• A valid "IF" statement can contain a singular code block or an alternate code block to run if the conditional expression is false ("IF/ELSE" statement).
• All "IF" statements must end with "END IF;" to indicate the end of the conditional block.

"IF" Statement:

IF (<insert-conditional-expression>) THEN
    <insert-code>
END IF;

"IF/ELSE" Statement:

IF (<insert-conditional-expression>) THEN
    <insert-code>
ELSE
    <insert-alternate-code>
END IF;

PRINT Statement

The "PRINT" statement is used to display output or information to the user. It allows the program to output values or text onto the screen or console.

• The "PRINT" statement can take any number of arguments.
• It accepts string literals, variables, and expressions, separated by commas.

Example:

INT r, h, addition, multiply;
r = 1;
h = 2;
addition = r + h; /* 3 */
multiply = r * h; /* 2 */
PRINT  ("The output results are: ", addition, " and ", multiply); /* returns "The output results are: 3 and 2" */

Exception handling

Exception handling occurs when errors are encountered during parsing or execution.

Types of Errors:

• Syntax Errors: Occurs when invalid syntax is encountered that does not conform to the language syntax.
• Runtime Exceptions: Occurs when invalid operations are performed, such as using an undeclared variable within the "PRINT" statement or using the NOT unary operator in the definition of an INT variable.