i'm redoing all the parsing lol
Jordan Orelli
8 months ago
parent
d152c4092a
commit
cd51f4cce1
@ -1,3 +1,98 @@
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# clyde
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A command-line shell. Initial development is for Windows because Windows has the worst starting point when it comes to CLI shells.
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A command-line shell. Initial development is for Windows because Windows has
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the worst starting point when it comes to CLI shells. Assuming nothing here
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works and it doesn't even compile.
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## Background
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The needs of this project reflect my professional experience working on
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multiplayer video games. Prior to working in the games industry, I worked in
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the web industry, primarily writing server software. The working practices of
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programmers in these industries differ substantially. The large differences in
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these working practices create a substantial and difficult social divide
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within studios that make multiplayer games. These social differences make an
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already-difficult category of software even more difficult to develop. The
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goal of this project is to reduce the tooling divide that exists between
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client and server developers at multiplayer game studios, with the expectation
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that shrinking this tooling gap can reduce the social divide that exists
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between game developers and server/infrastructure developers at game studios.
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### Windows is a hard requirement
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The first gap that appears within the greater software developer landscape is
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the question of using Windows at all. Let us dispense with this question
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immediately: Windows is a necesary tool within the game development industry.
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Supporting Windows is a hard requirement of this project.
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Many necessary tools, such as tools provided by game console manufacturers and
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tools that integrate with the dominant game engines (Unity and Unreal) only
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support Windows. If your reaction to this is "don't use those tools" or "make
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your game in Godot", please just stop. This is a very common reaction from
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professional programmers who have never worked in gamedev, who don't
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understand the constraints that most game developers face. Unfortunately a
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large portion of programming discussion happens on Hacker News, Reddit, and
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Lobsters, each of which uses a democratic structure.
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I will not attempt to convince you that Windows is broadly
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unavoidable in professional game development and that Windows is a necessary
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tool for game development studios, even studios that employ engineers for whom
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Windows is not necessary for their individual role. If you want to advocate
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for Linux superiority, please go bother Nintendo, Sony, Microsoft, etc, not
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individual game developers. If you really can't get over this and feel the
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need to yell at me, please walk a few hundred yards into a dense forest and
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scream your complaints into the wilderness to feel better.
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The command-line environments built into Windows are incredibly primitive.
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These environments are so primitive that millions of professional programmers
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who work primarily on Windows are led to believe that command-line
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environments themselves are *inherently* primitive.
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. The limitations of built-in
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command-line environments on Windows is so severe that there are entire
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categories of professional computer programmers who believe that they are "not
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terminal people", often without realizing that the terminal on Linux and MacOS
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is a vastly different experience and different tooling ecosystem than it is on
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Windows. Many professional Windows developers believe that CLI environments
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are inherently primitive, because their only exposure to CLI environments is
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through the built-in Windows shells.
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Windows ships with two built-in
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shells. The first shell is the Command Prompt, which we'll refer to as
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[cmd.exe](https://en.wikipedia.org/wiki/Cmd.exe) as it is colloquially known,
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even when running inside of
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[terminal.exe](https://en.wikipedia.org/wiki/Windows_Terminal). The second
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shell is [PowerShell](https://en.wikipedia.org/wiki/PowerShell).
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### Insufficiency of cmd.exe
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The insufficiency of cmd.exe is widely understood to people with experience
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with Unix-like operating systems such as Linux and MacOS, which typically
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include either [bash](https://en.wikipedia.org/wiki/Bash_(Unix_shell)) or
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[zsh](https://en.wikipedia.org/wiki/Z_shell). This insufficiency is severe
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enough that it drives people off of Windows entirely.
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In some industries, such as games, Windows is a required development
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environment, because many tools are available only on Windows. Free software
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purists who want to insist that you can make video games on Linux, please feel
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free to leave now, this project is not for you.
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## Terimology
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- **executable**: a shell built-in or an executable file (i.e., an .exe file)
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## examples
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$> a
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Find an executable named `a` somewhere on `PATH` and execute it in the
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foreground.
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$> ./a
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Use an executable named `a` within the current directory and execute it in the
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foreground. `a` must be a file in the current directory. If `a` would refer to
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both a shell built-in and a file in the current directory, use the file in the
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current directory.
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$>
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@ -0,0 +1,278 @@
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use crate::error::ParseError;
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use crate::lex::{Lexer, Token};
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use std::{
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cell::RefCell,
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collections::VecDeque,
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rc::{Rc, Weak},
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};
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#[derive(PartialEq)]
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pub enum Value {
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/// The start symbol of our parse tree. Each parse tree is rooted in a node whose value is the
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/// start symbol. This is the only node in the tree that should utilize the start symbol.
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Start,
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Statement,
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Terminal(Token),
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}
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impl Value {
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fn is_terminal(&self) -> bool {
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matches!(self, Value::Terminal(_))
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}
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}
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/// A node in a parse tree.
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pub struct Node {
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/// A node may or may not have a parent node. If a node does not have a parent node, that node
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/// is the root node of a tree.
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parent: Option<Weak<Node>>,
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/// The value of the element at this node
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value: Value,
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/// A node may or may not have children. Since an empty vector is a valid vector, a node
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/// without children is represented as having an empty children vector. A node having an empty
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/// list of children is a leaf node in a tree.
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children: RefCell<Vec<Rc<Node>>>,
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}
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impl Node {
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fn new() -> Cursor {
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let root = Node {
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parent: None,
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value: Value::Start,
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children: RefCell::new(Vec::new()),
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};
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let root = Rc::new(root);
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Cursor {
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target: Rc::clone(&root),
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root,
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}
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}
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}
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/// Cursor values expose access to a parse tree.
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struct Cursor {
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target: Rc<Node>,
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root: Rc<Node>,
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}
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impl Cursor {
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/// Climbs one level up a parse tree. The cursor is re-pointed from its current target node to
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/// the parent of its current target node. This method fails if the cursor is already at the
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/// root node of the parse tree.
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fn up(&mut self) -> Result<(), ParseError> {
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match &self.target.parent {
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None => Err(ParseError::AtRootAlready),
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Some(parent) => match parent.upgrade() {
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Some(parent) => {
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self.target = parent;
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Ok(())
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}
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None => Err(ParseError::ParentIsGone),
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},
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}
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}
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/// Adds a value to the children of the current target node, then descends to select that
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/// child.
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fn push(&mut self, v: Value) -> Result<(), ParseError> {
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if self.target.value.is_terminal() {
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return Err(ParseError::PushOntoTerminal);
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}
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let node = Node {
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parent: Some(Rc::downgrade(&self.target)),
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value: v,
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children: RefCell::new(Vec::new()),
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};
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let node = Rc::new(node);
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self.target
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.children
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.try_borrow_mut()?
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.push(Rc::clone(&node));
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self.target = node;
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Ok(())
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}
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fn is_root(&self) -> bool {
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self.target.parent.is_none()
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}
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fn into_root(self) -> Rc<Node> {
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Rc::clone(&self.root)
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}
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fn value(&self) -> &Value {
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&self.target.value
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}
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}
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struct Parser<'text> {
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source: Lexer<'text>,
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cursor: Cursor,
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}
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impl<'text> Parser<'text> {
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pub fn new(source: Lexer<'text>) -> Self {
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Self {
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source,
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cursor: Node::new(),
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}
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}
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pub fn parse(mut self) -> Result<Rc<Node>, ParseError> {
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while self.step()? {}
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Ok(self.cursor.into_root())
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}
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fn step(&mut self) -> Result<bool, ParseError> {
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match self.cursor.value() {
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Value::Start => self.step_start(),
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Value::Statement => self.step_statement(),
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Value::Terminal(_) => panic!(),
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}
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}
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fn step_start(&mut self) -> Result<bool, ParseError> {
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assert!(matches!(self.cursor.value(), Value::Start));
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match self.source.peek()? {
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Some(Token::String(_)) => {
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self.cursor.push(Value::Statement)?;
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let token = self.source.next().unwrap()?;
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self.cursor.push(Value::Terminal(token))?;
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self.cursor.up()?;
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Ok(true)
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}
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Some(Token::Glob(_)) => {
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let token = self.source.next().unwrap()?;
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Err(ParseError::UnexpectedToken(token))
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}
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None => Ok(false),
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}
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}
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fn step_statement(&mut self) -> Result<bool, ParseError> {
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assert!(matches!(self.cursor.value(), Value::Statement));
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match self.source.peek()? {
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Some(Token::String(_) | Token::Glob(_)) => {
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let token = self.source.next().unwrap()?;
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self.cursor.push(Value::Terminal(token))?;
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self.cursor.up()?;
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Ok(true)
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}
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None => Ok(false),
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}
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}
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}
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fn parse(source: &str) -> Result<Rc<Node>, ParseError> {
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let tokens = Lexer::new(source);
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let parser = Parser::new(tokens);
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parser.parse()
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}
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#[cfg(test)]
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mod test {
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use super::*;
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use crate::lex::lex;
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#[test]
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fn root() {
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let mut cursor = Node::new();
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assert!(cursor.up().is_err());
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assert!(cursor.target.value == Value::Start);
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assert!(cursor.is_root());
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}
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#[test]
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fn single_val() {
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let mut cursor = Node::new();
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let mut tokens = lex(" ls ").unwrap();
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let ls = tokens.pop().unwrap();
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assert!(cursor.push(Value::Statement).is_ok());
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assert!(cursor.push(Value::Terminal(ls.clone())).is_ok());
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assert!(cursor.push(Value::Terminal(ls.clone())).is_err());
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assert!(cursor.target.value == Value::Terminal(ls));
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assert!(!cursor.is_root());
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assert!(cursor.up().is_ok());
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assert!(cursor.up().is_ok());
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assert!(cursor.is_root());
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assert!(cursor.up().is_err());
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assert!(cursor.value() == &Value::Start);
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let root = cursor.into_root();
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assert!(root.value == Value::Start);
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}
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#[test]
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fn test_parse() -> Result<(), ParseError> {
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parse("ls")?;
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// parse("*")?;
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// parse("x* ls")?;
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Ok(())
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}
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}
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/*
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> ls
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start
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statement
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ls
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> ls ;
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start
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statement
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ls
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;
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> ls ; ls
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start
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statement
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ls
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;
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statement
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ls
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> ls one two three
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start
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statement
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ls
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one
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two
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three
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> ls > files.txt ; echo files.txt
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start
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statement
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ls
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>
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files.txt
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;
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statement
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echo
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files.txt
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> if exists ~/.vimrc : echo you have a vimrc
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> if $x == 3: echo hi
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start
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if
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expression
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$x
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==
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3
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:
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statement
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echo
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hi
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*/
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