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diff --git a/challenge-287/ppentchev/rust/src/bin/ch-2.rs b/challenge-287/ppentchev/rust/src/bin/ch-2.rs
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+++ b/challenge-287/ppentchev/rust/src/bin/ch-2.rs
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+#![deny(missing_docs)]
+#![deny(clippy::missing_docs_in_private_items)]
+// SPDX-FileCopyrightText: Peter Pentchev <roam@ringlet.net>
+// SPDX-License-Identifier: BSD-2-Clause
+//! PWC 287 task 2: Valid Number
+
+use std::env;
+use std::io;
+use std::process::{ExitCode, Termination};
+
+use anyhow::{Context, Result};
+use nom::{
+    branch::alt,
+    bytes::complete::tag,
+    character::complete::one_of,
+    combinator::{all_consuming, opt},
+    multi::{many0, many1},
+    sequence::tuple,
+    IResult,
+};
+use tracing::debug;
+
+/// The examples from the problem.
+const TEST_NUMBERS: [&str; 7] = ["1", "a", ".", "1.2e4.2", "-1.", "+1E-8", ".44"];
+
+/// The result of the main program or an invoked subcommand.
+enum MainResult {
+    /// Everything seems fine.
+    Ok,
+}
+
+impl Termination for MainResult {
+    fn report(self) -> ExitCode {
+        match self {
+            Self::Ok => ExitCode::SUCCESS,
+        }
+    }
+}
+
+/// Recognize a plus or minus sign at the start of the mantissa or the exponent.
+fn _p_sign(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = one_of("+-")(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize an ASCII decimal digit.
+fn _p_digit(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = one_of("0123456789")(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a decimal dot maybe followed by some digits.
+fn _p_large_fractional_part(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = tuple((tag("."), many0(_p_digit)))(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a number with some digits before the optional decimal dot, etc.
+fn _p_large_number(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = tuple((many1(_p_digit), opt(_p_large_fractional_part)))(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a number between 0 and 1: a decimal dot and some digits.
+fn _p_small_number(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = tuple((tag("."), many1(_p_digit)))(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a valid mantissa: sign, digits, decimal dot, etc.
+fn _p_mantissa(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = tuple((opt(_p_sign), alt((_p_large_number, _p_small_number))))(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a valid `[Ee][+-]?{digits}` exponent, return the unit value on success.
+fn _p_exponent(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = tuple((one_of("Ee"), opt(_p_sign), many1(_p_digit)))(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a valid number, return the unit value on success.
+fn _p_valid_number(input: &str) -> IResult<&str, ()> {
+    let (r_input, _) = all_consuming(tuple((_p_mantissa, opt(_p_exponent))))(input)?;
+    Ok((r_input, ()))
+}
+
+/// Recognize a valid number, return "true" or "false" as a string.
+#[tracing::instrument]
+fn valid_number(input: &str) -> Result<&'static str> {
+    debug!("Checking whether '{input}' is a valid number");
+    if _p_valid_number(input).is_ok() {
+        Ok("true")
+    } else {
+        Ok("false")
+    }
+}
+
+/// The main program - parse the environment settings, do something about it.
+#[allow(clippy::print_stdout)]
+fn main() -> Result<MainResult> {
+    if env::var("PWC_FROM_STDIN").unwrap_or_else(|_| String::new()) == "1" {
+        let mut line = String::new();
+        io::stdin()
+            .read_line(&mut line)
+            .context("Could not read a line from the standard input stream")?;
+        println!(
+            "{res}",
+            res = valid_number(line.trim_end_matches(&['\r', '\n']))?
+        );
+    } else {
+        for test_str in TEST_NUMBERS {
+            println!("{res}", res = valid_number(test_str)?);
+        }
+    }
+    Ok(MainResult::Ok)
+}