wip flat representation of polynomial over Z

src/poly/flat.rs

@@ -0,0 +1,181 @@
+use itertools::Itertools;
+use std::fmt::{self, Display};
+
+use std::ops::{Add, BitXor, Mul};
+
+use super::var::{StaticVar, Var};
+use std::collections::HashMap;
+
+#[derive(Clone, Debug)]
+pub struct Poly<V: Var> {
+    mono: HashMap<Mono<V>, i32>,
+}
+
+impl<V: Var> Default for Poly<V> {
+    fn default() -> Self {
+        Poly {
+            mono: Default::default(),
+        }
+    }
+}
+
+impl<V: Var> Display for Poly<V> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        match self.mono.is_empty() {
+            true => write!(fmt, "∅"),
+            false => write!(
+                fmt,
+                "{}",
+                self.mono
+                    .iter()
+                    .map(|(m, c)| format!("{}{}", c, m))
+                    .join(" + ")
+            ),
+        }
+    }
+}
+
+impl<V: Var, T: IntoIterator> From<T> for Poly<V>
+where
+    Poly<V>: FromIterator<<T as IntoIterator>::Item>,
+{
+    fn from(value: T) -> Self {
+        value.into_iter().collect()
+    }
+}
+
+impl<V: Var, U: Into<Mono<V>>> FromIterator<(i32, U)> for Poly<V> {
+    fn from_iter<T: IntoIterator<Item = (i32, U)>>(iter: T) -> Self {
+        Poly {
+            mono: iter.into_iter().map(|(c, m)| (m.into(), c)).collect(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+pub struct Mono<V: Var> {
+    pub term: Vec<(V, u32)>,
+}
+
+impl<V: Var, T: IntoIterator> From<T> for Mono<V>
+where
+    Mono<V>: FromIterator<<T as IntoIterator>::Item>,
+{
+    fn from(value: T) -> Self {
+        value.into_iter().collect()
+    }
+}
+
+impl<V: Var, U: Into<V>> FromIterator<(U, u32)> for Mono<V> {
+    fn from_iter<T: IntoIterator<Item = (U, u32)>>(iter: T) -> Self {
+        let mut term = iter
+            .into_iter()
+            .map(|(t, pow)| (t.into(), pow))
+            .collect::<Vec<(V, u32)>>();
+        term.sort();
+
+        // Check duplicate variables
+        assert!((term[..])
+            .windows(2)
+            .all(|window| window[0].0 != window[1].0));
+
+        Mono { term }
+    }
+}
+
+impl<V: Var> Display for Mono<V> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        write!(
+            fmt,
+            "{}",
+            self.term
+                .iter()
+                .map(|(t, p)| match p {
+                    1 => format!("{t}"),
+                    _ => format!("{t}^{p}"),
+                })
+                .join("")
+        )
+    }
+}
+
+impl BitXor<u32> for StaticVar {
+    type Output = Mono<StaticVar>;
+
+    fn bitxor(self, exp: u32) -> Self::Output {
+        [(self, exp)].into()
+    }
+}
+
+impl<'a> BitXor<u32> for &'a StaticVar {
+    type Output = Mono<StaticVar>;
+
+    fn bitxor(self, exp: u32) -> Self::Output {
+        [(self.clone(), exp)].into()
+    }
+}
+
+impl<V: Var> Mul for Mono<V> {
+    type Output = Self;
+
+    fn mul(self, other: Mono<V>) -> Self::Output {
+        let mut a_term = self.term.into_iter().peekable();
+        let mut b_term = other.term.into_iter().peekable();
+
+        let mut result: Vec<(V, u32)> = Default::default();
+
+        loop {
+            match (a_term.peek(), b_term.peek()) {
+                (Some((a_var, _)), Some((b_var, _))) => {
+                    if a_var < b_var {
+                        result.push(a_term.next().unwrap());
+                    } else if a_var > b_var {
+                        result.push(b_term.next().unwrap());
+                    } else {
+                        let (var, a_exp) = a_term.next().unwrap();
+                        let (_, b_exp) = b_term.next().unwrap();
+                        result.push((var, a_exp + b_exp));
+                    }
+                }
+                (Some(a), None) => {
+                    result.push(a.clone());
+                    a_term.next();
+                }
+                (None, Some(b)) => {
+                    result.push(b.clone());
+                    b_term.next();
+                }
+                (None, None) => {
+                    break;
+                }
+            }
+        }
+
+        Mono { term: result }
+    }
+}
+
+impl<V: Var> Mul<Mono<V>> for i32 {
+    type Output = Poly<V>;
+
+    fn mul(self, mono: Mono<V>) -> Self::Output {
+        let mut poly: HashMap<Mono<V>, i32> = Default::default();
+
+        poly.insert(mono, self);
+
+        Poly { mono: poly }
+    }
+}
+
+impl<V: Var> Add for Poly<V> {
+    type Output = Poly<V>;
+
+    fn add(mut self, other: Poly<V>) -> Self::Output {
+        for (mono, coeff) in other.mono {
+            let entry = self.mono.entry(mono).or_insert(0);
+            *entry += coeff;
+        }
+        self.mono.retain(|_, &mut coeff| coeff != 0);
+        self
+    }
+}