starting ebnf representation
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@ -7,6 +7,7 @@ mod parser;
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mod primitives;
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mod representation;
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mod sequence;
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mod util;
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#[cfg(test)]
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mod test;
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@ -1,12 +1,66 @@
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use std::fmt;
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use crate::util::intersperse_option;
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#[derive(Debug)]
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pub struct Representation {}
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pub struct Representation {
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production_output: EBNF,
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}
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impl Representation {
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pub fn show(&self) {
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println!("Not done");
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pub fn show(&self) -> String {
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self.production_output.to_string()
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}
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pub fn new() -> Self {
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Self {}
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Self {
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production_output: EBNF::None,
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}
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}
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pub fn with_production(production_output: EBNF) -> Self {
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Self { production_output }
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}
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}
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#[derive(Debug)]
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pub enum EBNF {
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None,
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CharTerminal(char),
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Alternation(Vec<EBNF>),
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}
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impl fmt::Display for EBNF {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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EBNF::None => write!(f, "none"),
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EBNF::CharTerminal(ch) => write!(f, "'{ch}'"),
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EBNF::Alternation(items) => {
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for item in intersperse_option(items.iter()) {
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match item {
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None => write!(f, " | ")?,
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Some(item) => write!(f, "{item}")?,
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}
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}
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write!(f, "")
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}
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_ebnf_print() {
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let example = EBNF::Alternation(vec![
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EBNF::CharTerminal('f'),
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EBNF::CharTerminal('a'),
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EBNF::CharTerminal('k'),
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EBNF::CharTerminal('e'),
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]);
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assert_eq!(example.to_string(), "'f' | 'a' | 'k' | 'e'");
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}
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}
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46
src/util.rs
Normal file
46
src/util.rs
Normal file
@ -0,0 +1,46 @@
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use std::iter::Peekable;
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pub(crate) fn intersperse_option<I: Iterator>(iterator: I) -> impl Iterator<Item = Option<I::Item>>
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where
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I::Item: Clone,
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{
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intersperse(iterator.map(Some), None)
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}
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pub(crate) fn intersperse<I: Iterator>(iterator: I, separator: I::Item) -> Intersperse<I>
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where
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I::Item: Clone,
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{
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Intersperse {
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inner: iterator.peekable(),
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separator,
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needs_sep: false,
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}
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}
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pub struct Intersperse<I>
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where
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I: Iterator,
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{
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inner: Peekable<I>,
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separator: I::Item,
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needs_sep: bool,
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}
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impl<I> Iterator for Intersperse<I>
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where
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I: Iterator,
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I::Item: Clone,
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{
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type Item = I::Item;
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fn next(&mut self) -> Option<Self::Item> {
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if self.needs_sep && self.inner.peek().is_some() {
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self.needs_sep = false;
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Some(self.separator.clone())
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} else {
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self.needs_sep = true;
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self.inner.next()
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}
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}
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}
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