brane_dsl/scanner/
comments.rs

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//  COMMENTS.rs
//    by Lut99
//
//  Created:
//    25 Aug 2022, 11:08:56
//  Last edited:
//    17 Jan 2023, 14:59:18
//  Auto updated?
//    Yes
//
//  Description:
//!   Defines a few scanning functions that parse comments.
//

use nom::bytes::complete as bc;
use nom::error::{ContextError, ParseError};
use nom::{IResult, Parser, branch, combinator as comb, sequence as seq};

use super::Span;
use super::tokens::Token;


/***** SCANNING FUNCTIONS *****/
/// Parses a single-line comment off the top of the given input.
///
/// # Arguments
/// - `input`: The input text to scan.
///
/// # Returns
/// The remaining tokens and a `Token::None`, representing that we did not really parse useful information.
///
/// # Errors
/// This function errors if we could not parse a comment.
pub fn single_line_comment<'a, E: ParseError<Span<'a>> + ContextError<Span<'a>>>(input: Span<'a>) -> IResult<Span<'a>, Token<'a>, E> {
    comb::value(Token::None, seq::pair(bc::tag("//"), seq::terminated(comb::opt(bc::is_not("\n")), branch::alt((bc::tag("\n"), comb::eof)))))
        .parse(input)
}

/// Parses a multi-line comment off the top of the given input.
///
/// # Arguments
/// - `input`: The input text to scan.
///
/// # Returns
/// The remaining tokens and a `Token::None`, representing that we did not really parse useful information.
///
/// # Errors
/// This function errors if we could not parse a comment.
pub fn multi_line_comment<'a, E: ParseError<Span<'a>> + ContextError<Span<'a>>>(input: Span<'a>) -> IResult<Span<'a>, Token<'a>, E> {
    comb::value(Token::None, seq::tuple((bc::tag("/*"), comb::cut(seq::pair(bc::take_until("*/"), bc::tag("*/")))))).parse(input)
}





/***** LIBRARY *****/
/// Scans a comment from the top of the given input.
///
/// # Arguments
/// - `input`: The input text to scan.
///
/// # Returns
/// The remaining tokens and a `Token::None`, representing that we did not really parse useful information.
///
/// # Errors
/// This function errors if we could not parse a comment.
pub fn parse<'a, E: ParseError<Span<'a>> + ContextError<Span<'a>>>(input: Span<'a>) -> IResult<Span<'a>, Token<'a>, E> {
    // println!("COMMENTS")
    branch::alt((single_line_comment, multi_line_comment)).parse(input)
}