Design a new programming language grammar

What a fascinating task!

Here's a design for a new programming language grammar, which we'll call "Nexa". Nexa is a statically-typed, object-oriented language with a focus on simplicity, readability, and expressiveness.

Syntax

Nexa's syntax is designed to be concise and easy to read. It uses a combination of keywords, symbols, and indentation to define the structure of programs.

Basic Syntax Elements

Identifiers: Names of variables, functions, and classes are written in camelCase (e.g., helloWorld).
Keywords: Reserved words that have special meanings in Nexa, such as class, function, if, else, etc.
Symbols: Special characters used to delimit code blocks, such as { and }, or to indicate operators, such as + and -.
Indentation: Used to denote block-level structure, such as function bodies or class definitions.

Lexical Structure

Nexa's lexical structure is composed of the following elements:

Tokens: The basic building blocks of Nexa's syntax, such as keywords, identifiers, symbols, and literals.
Token sequences: A sequence of tokens that forms a valid Nexa statement or expression.

Syntax Rules

Here are the basic syntax rules for Nexa:

Program: A Nexa program consists of one or more statements, separated by semicolons (;).
```
program {
 // statements
}
```
Statement: A statement is either a declaration, a function, or an expression.
```
statement ::= declaration | function | expression
```

Declaration: A declaration defines a variable, constant, or type.

declaration ::= "var" identifier type | "const" identifier literal | "type" identifier type

Function: A function defines a block of code that can be called multiple times.
```
function ::= "function" identifier "(" parameter-list ")" block
```
Parameter-list: A list of parameters passed to a function.
```
parameter-list ::= identifier ("," identifier)*
```
Block: A block of code, denoted by indentation.
```
block ::= "{" statement* "}"
```

Expression: An expression is a combination of values, operators, and functions.

expression ::= term ((ADD | SUB) term)*
term ::= factor ((MUL | DIV) factor)*
factor ::= identifier | literal | "(" expression ")"

Operators: Nexa supports the following operators:
- + (addition)
- - (subtraction)
- * (multiplication)
- / (division)
- = (assignment)
- == (equality)
- != (inequality)

Type System

Nexa has a statically-typed type system, which means that the type of every expression is known at compile-time. The type system is based on the following principles:

Primitive types: Nexa has the following primitive types:
- int: 32-bit signed integer
- float: 32-bit floating-point number
- bool: boolean value (true or false)
- string: Unicode string
Reference types: Nexa has the following reference types:
- class: a user-defined class
- interface: an interface that defines a set of methods
Type inference: Nexa infers the type of a variable or expression based on its usage.

Semantics

Nexa's semantics are defined by the following rules:

Evaluation: Expressions are evaluated in a left-to-right order.
Assignment: The assignment operator (=) assigns the value of the right-hand side to the left-hand side.
Control flow: Nexa supports the following control flow statements:
- if statement: executes a block of code if a condition is true
- else statement: executes a block of code if a condition is false
- while statement: executes a block of code while a condition is true
- for statement: executes a block of code for a specified number of iterations

Example Code

Here's an example of a simple Nexa program:

program {
    var x: int = 5;
    var y: int = 3;

    function add(a: int, b: int): int {
        return a + b;
    }

    print(add(x, y));
}

This program defines two variables x and y of type int, a function add that takes two int arguments and returns an int value, and a print statement that calls the add function and prints the result.

This is just a starting point, and Nexa's grammar can be refined and extended as needed. I hope this gives you a good idea of what a new programming language grammar might look like!

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