Map
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parent
194e23a5be
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32
src/lib.rs
32
src/lib.rs
@ -1,35 +1,51 @@
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#![feature(assert_matches)]
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#![allow(dead_code)] //TODO eventually turn this off
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type ParseResult<I, O, E> = Result<(O, I), E>;
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trait Parser<I, O, E> {
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fn parse(&self, input: I) -> ParseResult<I, O, E>;
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}
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impl<I, O, E, F> Parser<I, O, E> for F where F: Fn(I) -> ParseResult<I, O, E> {
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impl<I, O, E, F> Parser<I, O, E> for F
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where
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F: Fn(I) -> ParseResult<I, O, E>,
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{
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fn parse(&self, input: I) -> ParseResult<I, O, E> {
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self(input)
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}
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}
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fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, (), &str> {
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fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, &str> {
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move |input| match input.get(0..expected.len()) {
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Some(next) if next == expected =>
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Ok(((), &input[expected.len()..])),
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_ => Err(input)
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Some(next) if next == expected => Ok((expected, &input[expected.len()..])),
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_ => Err(input),
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}
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}
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fn map<P, F, I, O1, O2, E>(parser: P, map_fn: F) -> impl Parser<I, O2, E>
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where
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P: Parser<I, O1, E>,
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F: Fn(O1) -> O2,
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{
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move |input| parser.parse(input).map(|(result, rest)| (map_fn(result), rest))
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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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use std::assert_matches::assert_matches;
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#[test]
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fn parsing() {
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fn test_parsing() {
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let output = literal("a")("a yolo");
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assert_matches!(output.unwrap(), ((), " yolo"));
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assert_matches!(output.unwrap(), ("a", " yolo"));
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}
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#[test]
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fn test_map() {
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let lit_a = literal("a");
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let output = map(lit_a, |s| s.to_uppercase()).parse("a yolo");
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assert_matches!(output.unwrap(), (s, " yolo") if s == "A");
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}
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}
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