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use super::interp::{ByteCode, OpCode, WordCatalog, WordList};
use std::collections::HashMap;
use std::iter::{Enumerate, Iterator};
use std::str::Chars;
#[derive(Debug)]
pub enum ParseError {
EOF,
NameStackEmpty,
MissingQuote,
UnknownWord(String),
}
impl std::fmt::Display for ParseError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::EOF => write!(f, "premature end-of-file"),
Self::NameStackEmpty => write!(f, "name stack empty"),
Self::MissingQuote => write!(f, "missing ending quote"),
Self::UnknownWord(word) => write!(f, "unknown word: {}", word),
}
}
}
impl std::error::Error for ParseError {}
type ParseResult<T> = Result<T, ParseError>;
#[derive(Debug)]
pub struct Parser<'a> {
text: &'a str,
enumerator: Enumerate<Chars<'a>>,
wordlist: WordList,
wordalog: WordCatalog<'a>,
namestack: Vec<&'a str>,
}
impl<'a> Parser<'a> {
pub fn new(text: &'a str) -> Self {
let enumerator = text.chars().enumerate();
let mut wl = vec![];
// main routine is always the first entry.
wl.push(ByteCode(vec![]));
Self {
text,
enumerator,
wordlist: WordList(wl),
wordalog: WordCatalog(HashMap::new()),
namestack: vec![],
}
}
// pull the next, whitespace-delimited word off the input stream.
fn next_word(&mut self) -> Option<(&'a str, usize, usize)> {
let mut start = 0;
let chars =
self.enumerator.by_ref()
.skip_while(|(i, c)| {
start = *i;
return c.is_whitespace()
});
for (i, c) in chars {
if c.is_whitespace() {
let end = i;
let word = self.text.get(start..end).unwrap();
return Some((word, start, end))
}
}
None
}
// push `op` onto the currently building bytecode, as determined
// by the top of the `namestack`.
fn bc_push(&mut self, op: OpCode) -> ParseResult<()> {
let word_index = match self.namestack.last() {
None => &0,
Some(name) => self.wordalog.0.get(name).ok_or(ParseError::NameStackEmpty)?,
};
self.wordlist.0[*word_index].0.push(op);
Ok(())
}
fn parse(&mut self) -> ParseResult<()> {
while let Some((word, _start, end)) = self.next_word() {
if let Ok(i) = word.parse::<i32>() {
self.bc_push(OpCode::Num(i))?;
} else if let Some(i) = self.wordalog.0.get(word) {
self.bc_push(OpCode::Call(*i))?;
} else {
match word {
r#"s""# => {
let (s_end, _) =
self.enumerator
.find(|(_i, c)| return *c == '"')
.ok_or(ParseError::MissingQuote)?;
self.bc_push(OpCode::Str(end+1, s_end))?;
},
":" => {
let (name, _, _) = self.next_word().ok_or(ParseError::EOF)?;
self.namestack.push(name);
self.wordalog.0.insert(name, self.wordlist.0.len());
self.wordlist.0.push(ByteCode(vec![]));
},
";" => {
self.bc_push(OpCode::Ret)?;
self.namestack.pop();
},
"+" => self.bc_push(OpCode::Add)?,
"-" => self.bc_push(OpCode::Sub)?,
other => return Err(ParseError::UnknownWord(String::from(other))),
}
}
}
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
use super::super::interp::OpCode;
fn parser_for(text: &str) -> Parser {
let mut p = Parser::new(text);
p.parse().expect("badparse");
p
}
#[test]
fn literal_num() {
let p = parser_for("1\n");
let main = &p.wordlist.0[0];
assert_eq!(main.len(), 1);
assert_eq!(main[0], OpCode::Num(1));
}
#[test]
fn literal_string() {
let p = parser_for(r#"s" hello there""#);
let main = &p.wordlist.0[0];
assert_eq!(main.len(), 1);
assert_eq!(main[0], OpCode::Str(3, 14));
}
#[test]
fn add_opcode() {
let p = parser_for("+\n");
let main = &p.wordlist.0[0];
eprintln!("main {:?}", main);
assert_eq!(main.len(), 1);
assert_eq!(main[0], OpCode::Add);
}
#[test]
fn sub_opcode() {
let p = parser_for("-\n");
let main = &p.wordlist.0[0];
eprintln!("main {:?}", main);
assert_eq!(main.len(), 1);
assert_eq!(main[0], OpCode::Sub);
}
#[test]
fn def_word() {
let p = parser_for(": add2 2 + ; 3 add2\n");
let main = &p.wordlist.0[0];
eprintln!("main {:?}", main);
let add2_index = p.wordalog.0.get("add2").expect("add2 has entry in wordlist");
let add2 = &p.wordlist.0[*add2_index];
eprintln!("add2 {:?}", add2);
assert_eq!(main.len(), 2);
assert_eq!(main[0], OpCode::Num(3));
assert_eq!(main[1], OpCode::Call(*add2_index));
assert_eq!(add2.len(), 3);
assert_eq!(add2[0], OpCode::Num(2));
assert_eq!(add2[1], OpCode::Add);
assert_eq!(add2[2], OpCode::Ret);
}
}
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