🖥️ ☕ Simple Interpreter ☕ 🖥️

This is an interpreter written in Java for my custom programming language, which I named "Simple." The Simple language supports variables, if statements, loops, and more.

Demo

Click here for a video demo 📹

How You Can Run It

Inside the executable folder, you’ll find SimpleInterpreter.jar. This JAR file can be used to run my interpreter. Since the interpreter is built in Java, you’ll need Java installed on your system.

After downloading SimpleInterpreter.jar, open a terminal in the same folder as the JAR file and run the following command:

java -jar SimpleInterpreter.jar

The interpreter will prompt you for the name of the .simple file you want to run. This repository includes several example programs you can try: main.simple, greeting.simple, wordGuesser.simple, and hangman.simple.

Simple Programming Language Features

Variables:

There are three types of variables in Simple:

• num – a number
• text – a string of text
• bool – a boolean value (TRUE or FALSE)

Variables are declared by writing the type, the variable name, an equals sign, and an expression.

Here are some examples:

text hello = ( "hi" );

bool yes = ( TRUE );

num age = ( 18 );

Note: Parentheses are required around expressions. They tell the interpreter that the value should or could be evaluated. Spaces are also required.

Text values must be wrapped in quotation marks (e.g., "hi").

Every statement ends with a semicolon (;).

If Statements:

Here’s an example of an if statement:

num age = ( 30 );
if ( age > 65 ); then;
  printLine ( "Hello elderly person!" );
  end;
else; then;
  printLine ( "Hello young person!" );
  end;

Be sure to include the parentheses in the expression after the if keyword, as well as spaces.

Use then; to begin the if block and end; to close it. Optionally, you can include an else; then; block, which must also be closed with end;.

Repeat Loops:

Here’s an example of a repeat loop:

repeat ( 10 ) i; then;
  printLine ( i );
  end;

After repeat and an expression defining the number of times to loop, you define an index variable (e.g., i) that keeps track of the iteration count. Everything between then; and end; is inside the loop.

Print Statements:

Use print and printLine to display text in the console. print does not add a new line, while printLine does.

Example:

print ( "hello" );
printLine ( "Hi" );

User Input:

Use input to get user input from the console. Assign the input to a text variable. The content within the given text variable will be replaced with the user input.

Example:

text name = ( "" );

print ( "Type your name: " );
input name;

printLine ( "Hello " + name + "!" );

Characters Within Strings:

Use characterAt to get a specific character from a string. Provide:

• The variable to store the result
• The index of the character as an expression
• The text to extract from as an expression

Example:

text name = ( "Daniel" );
text character = ( "" );

characterAt character ( 0 ) ( name );

printLine ( "The first letter of your name is: " + character );

Exiting:

Use the exit keyword to immediately terminate the program.

In this example, "Hello" will not be printed as the program is terminated before the print statement:

exit;

printLine ( "Hello" );