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//! > **An extremely flexible lexer/parser (get it?) for writing your own programming language**
//!
//! ## Elements of the `flexar` crate
//! - **Compiler Errors**
//! - **File positions**
//! - **Lexer generation macro**
//! - **Parser generation macros**
//! - (You'll have to implement the compiling / interpreting part of the language yourself)
//!
//! # Example
//! The following is an exapmle implementation of the flexar crate to create a simple math interpreter with support for varibles
//!
//! **example.fx**
//! ```psudeo
//! 6 / 1 + 2 * 3;
//! (1 + 2) * 3 + 4 / 5 - -3;
//! --5;
//! 1.2 * 4.29 / 36; // yoo even comments work :D
//! -12 + 34 / -3.4;
//! let a-value = 23 * 4;
//! a-value - 92;
//! ```
//! ## Code to execute the above code
//! ```rust
//! use std::collections::HashMap;
//! use flexar::prelude::*;
//!
//! //////////////////////////
//! // Errors
//! //////////////////////////
//!
//! flexar::compiler_error! {
//! [[Define] Errors]
//! (E001) "unexpected character": "character `", "` is unexpected";
//! (E002) "string not closed": "expected `\"` to close string";
//! (E003) "expected number": "expected number, found `", "`.";
//! (E004) "expected an expr": "expected expr, found `", "`.";
//! (E005) "expected `+` or `-` in binary operation": "expected `+` or `-`, found `", "`.";
//! (E006) "unexpected token": "unexpected token `", "`.";
//! (E007) "unclosed parentheses": "expected `)` to close parentheses";
//! (E008) "expected identifier in `let` statement": "expected ident, found `", "`.";
//! (E009) "expected `=` in `let` statement": "expected `=`, found `", "`.";
//! (E010) "expected one of `;`, `+`, `-`, `/` or `*`.": "expected `;` or operation, found `", "`.";
//! (RT001) "non-existant varible": "varible `", "` doesn't exist";
//! }
//!
//! //////////////////////////
//! // Lexer
//! //////////////////////////
//!
//! flexar::lexer! {
//! [[Token] lext, current, 'cycle]
//! else flexar::compiler_error!((E001, lext.position()) current).throw();
//!
//! token_types {
//! LParen => "(";
//! RParen => ")";
//! Int(val: u32) => val;
//! Float(val: f32) => val;
//! Plus => "+";
//! Minus => "-";
//! Mul => "*";
//! Div => "/";
//! Let => "let";
//! EQ => "=";
//! Semi => ";";
//! Ident(val: String) => val;
//! }
//!
//! Plus: +;
//! LParen: '(';
//! RParen: ')';
//! Minus: '-';
//! Mul: *;
//! EQ: =;
//! Semi: ;;
//! [" \n\t"] >> ({ lext.advance(); lext = lext.spawn(); continue 'cycle; });
//!
//! / child {
//! advance: current;
//! ck (current, /) {
//! rsome current {
//! { if current == '\n' { lext = child; continue 'cycle } };
//! };
//! };
//! advance:();
//! done Div();
//! };
//!
//! ["abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_"] child {
//! set ident { String::new() };
//! rsome (current, 'ident) {
//! set matched false;
//! ck (current, ["abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-0123456789"]) {
//! mut matched true;
//! { ident.push(current) };
//! };
//! { if !matched { break 'ident } };
//! };
//! if (ident == "let") { done Let(); };
//! done Ident(ident);
//! };
//!
//! ["0123456789"] child {
//! set number { String::new() };
//! set dot false;
//! rsome (current, 'number) {
//! set matched false;
//! ck (current, ["0123456789"]) {
//! mut matched true;
//! { number.push(current) };
//! };
//! ck (current, '.') {
//! if (dot) {
//! done Float(number.parse().unwrap());
//! };
//! mut matched true;
//! mut dot true;
//! { number.push(current) };
//! };
//! {if !matched {break 'number}};
//! };
//! if (dot) { done Float(number.parse().unwrap()); };
//! done Int(number.parse().unwrap());
//! };
//! }
//!
//! //////////////////////////
//! // Parser
//! //////////////////////////
//!
//! #[derive(Debug)]
//! pub enum Stmt {
//! Expr(Node<Expr>),
//! Let(String, Node<Expr>),
//! }
//!
//! #[derive(Debug)]
//! pub enum Expr {
//! Plus(Node<Factor>, Box<Node<Expr>>),
//! Minus(Node<Factor>, Box<Node<Expr>>),
//! Factor(Node<Factor>),
//! }
//!
//! #[derive(Debug)]
//! pub enum Factor {
//! Mul(Node<Number>, Box<Node<Factor>>),
//! Div(Node<Number>, Box<Node<Factor>>),
//! Number(Node<Number>),
//! }
//!
//! #[derive(Debug)]
//! pub enum Number {
//! Get(String),
//! Neg(Box<Node<Number>>),
//! Expr(Box<Node<Expr>>),
//! Int(u32),
//! Float(f32),
//! }
//!
//! #[derive(Debug)]
//! pub enum ProgramFile {
//! Single(Node<Stmt>),
//! Program(Box<[Node<Stmt>]>),
//! }
//!
//! flexar::parser! {
//! [[Number] parxt: Token]
//! parse {
//! (Ident(x)) => (Get(x.clone()));
//! (Plus), [number: Number::parse] => [number];
//! (Minus), [number: Number::parse] => (Neg(Box::new(number)));
//! (Int(x)) => (Int(*x));
//! (Float(x)) => (Float(*x));
//! (LParen) => {
//! [expr: Expr::parse] => {
//! (RParen) => (Expr(Box::new(expr)));
//! } (else Err(E007))
//! };
//! } else Err(E003: parxt.current_token());
//! }
//!
//! flexar::parser! {
//! [[Factor] parxt: Token]
//! parse {
//! [left: Number::parse] => {
//! (Mul), [right: Factor::parse] => (Mul(left, Box::new(right)));
//! (Div), [right: Factor::parse] => (Div(left, Box::new(right)));
//! } (else Ok(Factor::Number(left)))
//! } else Other(Number Number::parse(parxt));
//! }
//!
//! flexar::parser! {
//! [[Expr] parxt: Token]
//! parse {
//! [left: Factor::parse] => {
//! (Plus), [right: Expr::parse] => (Plus(left, Box::new(right)));
//! (Minus), [right: Expr::parse] => (Minus(left, Box::new(right)));
//! } (else Ok(Expr::Factor(left)))
//! } else Err(E004: parxt.current_token());
//! }
//!
//! flexar::parser! {
//! [[Stmt] parxt: Token]
//! parse {
//! [expr: Expr::parse] => (Expr(expr));
//! (Let) => {
//! (Ident(ident)) => {
//! (EQ), [expr: Expr::parse] => (Let(ident.clone(), expr));
//! } (else Err(E009: parxt.current_token()))
//! } (else Err(E008: parxt.current_token()))
//! } else Err(E006: parxt.current_token());
//! }
//!
//! flexar::parser! {
//! [[ProgramFile] parxt: Token]
//! single {
//! [stmt: Stmt::parse] => {
//! (Semi) => (Single(stmt));
//! } (else Err(E010: parxt.current_token()))
//! } else Err(E006: parxt.current_token());
//! }
//!
//! impl ProgramFile {
//! pub fn parse(tokens: &[token_node::Token<Token>]) -> Option<Self> {
//! if tokens.len() == 0 { return None }
//!
//! let mut parxt = Parxt::new(tokens);
//! let mut stmts = Vec::new();
//!
//! while parxt.current().is_some() {
//! match Self::single(&mut parxt) {
//! Ok(Node { node: Self::Single(x), .. }) => stmts.push(x),
//! Err((_, x)) => x.throw(),
//! _ => panic!("not possible"),
//! }
//! }
//!
//! Some(Self::Program(stmts.into_boxed_slice()))
//! }
//! }
//!
//! //////////////////////////
//! // Interpreter
//! //////////////////////////
//!
//! pub struct VisitCtx(HashMap<String, f32>, Position);
//! pub trait Visit {
//! fn visit(&self, visit_ctx: &mut VisitCtx) -> f32;
//! }
//!
//! impl ProgramFile {
//! pub fn visit(&self) {
//! if let Self::Program(stmts) = self {
//! let mut visit_ctx = VisitCtx(HashMap::new(), stmts[0].position.clone());
//! stmts.iter()
//! .for_each(|x| {x.visit(&mut visit_ctx);});
//! }
//! }
//! }
//!
//! impl<N: Visit + std::fmt::Debug> Visit for Node<N> {
//! fn visit(&self, visit_ctx: &mut VisitCtx) -> f32 {
//! visit_ctx.1 = self.position.clone();
//! self.node.visit(visit_ctx)
//! }
//! }
//!
//! impl Visit for Number {
//! fn visit(&self, visit_ctx: &mut VisitCtx) -> f32 {
//! use Number as N;
//! match self {
//! N::Int(x) => *x as f32,
//! N::Neg(x) => -x.visit(visit_ctx),
//! N::Float(x) => *x,
//! N::Get(x) => *visit_ctx.0.get(x).unwrap_or_else(||
//! compiler_error!((RT001, visit_ctx.1.clone()) x).throw()
//! ),
//! N::Expr(x) => x.visit(visit_ctx)
//! }
//! }
//! }
//!
//! impl Visit for Factor {
//! fn visit(&self, visit_ctx: &mut VisitCtx) -> f32 {
//! use Factor as F;
//! match self {
//! F::Mul(a, b) => a.visit(visit_ctx) * b.visit(visit_ctx),
//! F::Div(a, b) => a.visit(visit_ctx) / b.visit(visit_ctx),
//! F::Number(x) => x.visit(visit_ctx),
//! }
//! }
//! }
//!
//! impl Visit for Expr {
//! fn visit(&self, visit_ctx: &mut VisitCtx) -> f32 {
//! use Expr as E;
//! match self {
//! E::Factor(x) => x.visit(visit_ctx),
//! E::Plus(a, b) => a.visit(visit_ctx) + b.visit(visit_ctx),
//! E::Minus(a, b) => a.visit(visit_ctx) - b.visit(visit_ctx),
//! }
//! }
//! }
//!
//! impl Visit for Stmt {
//! fn visit(&self, visit_ctx: &mut VisitCtx) -> f32 {
//! use Stmt as S;
//! match self {
//! S::Expr(x) => println!("{}", x.visit(visit_ctx)),
//! S::Let(key, x) => {
//! let value = x.visit(visit_ctx);
//! visit_ctx.0.insert(key.clone(), value);
//! },
//! }
//!
//! 0f32 // means nothing
//! }
//! }
//!