brainterpreter 0.1.2

An interpreter for a Bauble toy programming language
Documentation 
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//! Abstract syntax tree

use crate::ast::Expression::{BinaryOperation, NumberLiteral, UnaryOperation};

#[derive(Debug, Clone, PartialEq)]
pub enum BinaryOperator {
    Add,
    Sub,
    Mul,
    Div,
    Equal,
    NotEqual,
    Less,
    Greater,
    LessOrEqual,
    GreaterOrEqual,
}

#[derive(Debug, Clone, PartialEq)]
pub enum UnaryOperator {
    Not,
    Negate,
}

#[derive(Debug, Clone, PartialEq, Default)]
pub struct Program {
    statements: Vec<Statement>,
}

#[derive(Debug, Clone, PartialEq)]
pub enum Expression {
    Nil,
    NumberLiteral(f64),
    BooleanLiteral(bool),
    StringLiteral(String),
    /// Access to array-like variable element by index
    Index {
        array: Box<Expression>,
        index: Box<Expression>,
    },
    Variable(String),
    AssignVariable(String, Box<Expression>),
    AssignIndexVariable {
        variable: String,
        index: Box<Expression>,
        value: Box<Expression>,
    },
    Array {
        initial: Box<Expression>,
        size: Box<Expression>,
    },
    FunctionCall(String, Vec<Expression>),
    BinaryOperation(BinaryOperator, Box<Expression>, Box<Expression>),
    UnaryOperation(UnaryOperator, Box<Expression>),
}

/// Represents a statement of the language
#[derive(Debug, Clone, PartialEq)]
pub enum Statement {
    Expression(Expression),
    DeclareVariable(String),
    DefineVariable(String, Expression),
    Function(String, Vec<String>, Box<Statement>),
    Print(Expression),
    Block(Vec<Statement>),
    If(Expression, Box<Statement>, Option<Box<Statement>>),
    While(Expression, Box<Statement>),
    Return(Expression),
}

impl Program {
    pub fn new(statements: Vec<Statement>) -> Self {
        Program { statements }
    }

    pub fn add_statement(&mut self, statement: Statement) {
        self.statements.push(statement);
    }

    pub fn statements(&self) -> &[Statement] {
        &self.statements
    }
}

impl Expression {
    pub fn binary(op: BinaryOperator, lhs: Expression, rhs: Expression) -> Self {
        BinaryOperation(op, Box::new(lhs), Box::new(rhs))
    }

    pub fn unary(op: UnaryOperator, lhs: Expression) -> Self {
        UnaryOperation(op, Box::new(lhs))
    }

    pub fn number(n: impl Into<f64>) -> Self {
        NumberLiteral(n.into())
    }

    pub fn variable(name: &str) -> Self {
        Expression::Variable(name.to_string())
    }
}

impl Statement {
    pub fn expression(expr: Expression) -> Self {
        Statement::Expression(expr)
    }

    pub fn function(name: &str, args: &[&str], body: Statement) -> Self {
        let args = args.iter().map(|s| s.to_string()).collect();
        Statement::Function(name.to_string(), args, Box::new(body))
    }

    pub fn if_statement(condition: Expression, then_branch: Statement) -> Self {
        Statement::If(condition, Box::new(then_branch), None)
    }

    pub fn if_else_statement(
        condition: Expression,
        then_branch: Statement,
        else_branch: Statement,
    ) -> Self {
        Statement::If(
            condition,
            Box::new(then_branch),
            Some(Box::new(else_branch)),
        )
    }

    pub fn while_loop(expr: Expression, body: Statement) -> Self {
        Statement::While(expr, Box::new(body))
    }

    pub fn print(expr: Expression) -> Self {
        Statement::Print(expr)
    }
}