Add forgotten solutions

aufgaben/sheet10/sol2/src/cmd/choose.rs

@@ -0,0 +1,63 @@
+//! This subcommand chooses items from a list.
+//!
+
+use clap::{Arg, ArgMatches, App, SubCommand};
+use rand::{self, Rng};
+use std::error::Error;
+
+pub fn clap() -> App<'static, 'static> {
+    SubCommand::with_name("choose")
+        .about("Chooses one or more values from a list")
+        .arg(
+            Arg::with_name("count")
+                .long("count")
+                .short("c")
+                .help("How many elements to choose")
+                .takes_value(true)
+                .validator(|s| {
+                    s.parse::<u64>()
+                        .map_err(|e| e.to_string())
+                        .and_then(|n| {
+                            if n == 1 {
+                                Err("number is smaller than 2".into())
+                            } else {
+                                Ok(())
+                            }
+                        })
+                })
+        )
+        .arg(
+            Arg::with_name("ELEMENTS")
+                .help("The list to choose one item from (comma separated)")
+                .required(true)
+                .multiple(true)
+        )
+}
+
+pub fn exec(matches: &ArgMatches) -> Result<String, Box<Error>> {
+    // Retrieve arguments
+    let count = value_t!(matches, "count", u64).unwrap_or(1);
+    let mut elements = values_t!(matches, "ELEMENTS", String).unwrap();
+
+    // Sanity check arguments
+    if count > elements.len() as u64 {
+        return Err("'count' argument is greater than the number of given elements".into());
+    }
+
+    let mut rng = rand::thread_rng();
+
+    // Choose a random valid index, remove the respective element from the
+    // input vector and insert it into the out vector. Repeat specified number
+    // of times.
+    let mut out = Vec::with_capacity(count as usize);
+    for _ in 0..count {
+        let idx = rng.gen_range(0, elements.len());
+        out.push(elements.swap_remove(idx));
+    }
+
+    if count == 1 {
+        Ok(out[0].to_string())
+    } else {
+        Ok(format!("{:?}", out))
+    }
+}

aufgaben/sheet10/sol2/src/cmd/coin.rs

@@ -0,0 +1,23 @@
+//! This subcommand flips a coin, returning either 'heads' or 'tails'
+//!
+
+use clap::{ArgMatches, App, SubCommand};
+use rand::{self, Rng};
+use std::error::Error;
+
+
+pub fn clap() -> App<'static, 'static> {
+    SubCommand::with_name("coin")
+        .about("Flips a coin, returning either 'heads' or 'tails'")
+
+}
+
+pub fn exec(_: &ArgMatches) -> Result<String, Box<Error>> {
+    let out = if rand::thread_rng().gen() {
+        "heads"
+    } else {
+        "tails"
+    };
+
+    Ok(out.into())
+}

aufgaben/sheet10/sol2/src/cmd/dice.rs

@@ -0,0 +1,36 @@
+//! This subcommand rolls a dice with a configurable number of sides, returning
+//! the number of the rolled dice.
+//!
+
+use clap::{Arg, ArgMatches, App, SubCommand};
+use rand::{self, Rng};
+use std::error::Error;
+
+pub fn clap() -> App<'static, 'static> {
+    SubCommand::with_name("dice")
+        .about("Rolls a dice")
+        .arg(
+            Arg::with_name("sides")
+                .long("sides")
+                .help("The number of sides of the dice")
+                .takes_value(true)
+                .validator(|s| {
+                    s.parse::<u64>()
+                        .map_err(|e| e.to_string())
+                        .and_then(|n| {
+                            if n <= 1 {
+                                Err("number is smaller than 2".into())
+                            } else {
+                                Ok(())
+                            }
+                        })
+                })
+        )
+}
+
+pub fn exec(matches: &ArgMatches) -> Result<String, Box<Error>> {
+    let sides = value_t!(matches, "sides", u64).unwrap_or(6);
+
+    let num = rand::thread_rng().gen_range(1, sides);
+    Ok(num.to_string())
+}

aufgaben/sheet10/sol2/src/cmd/mod.rs

@@ -0,0 +1,10 @@
+//! Contains all subcommands.
+//!
+//! Each subcommand's module has a `clap()` function which returns the clap
+//! structure describing the subcommand's command line use. The `exec()`
+//! function of each module executes the actual algorithm.
+//!
+
+pub mod dice;
+pub mod coin;
+pub mod choose;

aufgaben/sheet10/sol2/src/main.rs

@@ -0,0 +1,90 @@
+//! Flip -- command line utility for randomness tools
+//!
+//! This is a simple application which offers several small tools related to
+//! randomness. It uses the crates `clap` and `rand` for argument parsing and
+//! random number generation, respectively. Example usage:
+//!
+//! ```
+//! $ flip coin
+//! heads
+//! $ flip dice --sides=10
+//! 7
+//! $ flip choose --count=2 Peter Ursula Jürgen
+//! ["Peter", "Jürgen"]
+//! $ flip --times=3 coin
+//! heads
+//! heads
+//! tails
+//! ```
+
+#[macro_use]
+extern crate clap;
+extern crate rand;
+
+mod cmd;
+
+use clap::{Arg, App, AppSettings};
+use std::str::FromStr;
+use std::error::Error;
+
+
+/// Does most of the work: parses the command line args and executes the
+/// subcommand.
+fn parse_and_exec() -> Result<(), Box<Error>> {
+    let matches = App::new("Flip")
+        .version(crate_version!())
+        .author(crate_authors!())
+        .about("Offers several tools related to randomness")
+        .setting(AppSettings::SubcommandRequired)
+        .arg(
+            Arg::with_name("times")
+                .short("t")
+                .long("times")
+                .takes_value(true)
+                .validator(validate_parse::<u64>)
+                .help("Executes the specified subcommand the given number of times")
+        )
+        .subcommand(cmd::coin::clap())
+        .subcommand(cmd::dice::clap())
+        .subcommand(cmd::choose::clap())
+        .get_matches();
+
+    // Check what subcommand has been executed and fetch the matching
+    // function and sub-matches.
+    let (cmd_fn, sub_matches): (fn(_) -> _, _) = match matches.subcommand() {
+        ("coin",   sub_matches) => (cmd::coin::exec,   sub_matches.unwrap()),
+        ("dice",   sub_matches) => (cmd::dice::exec,   sub_matches.unwrap()),
+        ("choose", sub_matches) => (cmd::choose::exec, sub_matches.unwrap()),
+        _ => unreachable!("We enabled 'SubcommandRequired' for clap!"),
+    };
+
+    // We validate the string above. Thus, this will be an `Err` iff the
+    // argument wasn't specified. In this case it defaults to 1.
+    let times = value_t!(matches, "times", u64).unwrap_or(1);
+
+    // Execute the sub command the specified number of times, printing
+    // every result
+    for _ in 0..times {
+        let s = cmd_fn(sub_matches)?;
+        println!("{}", s);
+    }
+
+    Ok(())
+}
+
+fn main() {
+    let res = parse_and_exec();
+    if let Err(e) = res {
+        println!("{}", e);
+    }
+}
+
+/// Validator shorthand to check if a string is parsable as given type.
+fn validate_parse<T>(s: String) -> Result<(), String>
+    where T: FromStr,
+          T::Err: ToString,
+{
+    s.parse::<T>()
+        .map(|_| ())
+        .map_err(|e| e.to_string())
+}