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use std::collections::HashMap;
use std::fmt;
pub trait MachineRegister {
fn read(&self, key: char) -> i32;
fn write(&mut self, key: char, value: i32);
fn increment(&mut self, key: char, by: i32) {
self.write(key, self.read(key) + by)
}
}
#[derive(Debug)]
pub struct HashMapRegister {
registers: HashMap<char, i32>,
}
impl HashMapRegister {
pub fn new() -> Self {
HashMapRegister {
registers: HashMap::new(),
}
}
}
impl MachineRegister for HashMapRegister {
fn read(&self, key: char) -> i32 {
*self.registers.get(&key).unwrap_or(&0)
}
fn write(&mut self, key: char, value: i32) {
*self.registers.entry(key).or_insert(0) = value;
}
}
impl Default for HashMapRegister {
fn default() -> Self {
HashMapRegister::new()
}
}
impl fmt::Display for HashMapRegister {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut keys: Vec<char> = self.registers.keys().copied().collect();
keys.sort_unstable();
write!(f, "[")?;
for (i, key) in keys.iter().enumerate() {
if i != 0 {
write!(f, ", ")?;
}
write!(f, "{}={}", key, self.read(*key))?;
}
write!(f, "]")
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_read_empty_register() {
let registers = HashMapRegister::new();
assert_eq!(registers.read('a'), 0);
}
#[test]
fn test_write_and_read_register() {
let mut registers = HashMapRegister::new();
registers.write('a', 10);
assert_eq!(registers.read('a'), 10);
}
#[test]
fn test_increment_empty_register() {
let mut registers = HashMapRegister::new();
registers.increment('a', 5);
assert_eq!(registers.read('a'), 5);
}
#[test]
fn test_increment_non_empty_register() {
let mut registers = HashMapRegister::new();
registers.write('a', 5);
registers.increment('a', 5);
assert_eq!(registers.read('a'), 10);
}
#[test]
fn test_format_register() {
let mut registers = HashMapRegister::new();
registers.write('a', 10);
registers.write('d', -5);
registers.write('c', 12);
registers.write('b', 0);
assert_eq!(format!("{}", registers), "[a=10, b=0, c=12, d=-5]");
}
}