check if pval == val and abort subsequently

src/main.rs

@@ -14,11 +14,17 @@ trait Context {
 
 /// Simple Context will return it's value for any variable name
 impl Context for f64 {
-    fn get(&self, name: &str) -> Option<f64> {
+    fn get(&self, _: &str) -> Option<f64> {
         Some(*self)
     }
 }
 
+impl Context for () {
+    fn get(&self, _: &str) -> Option<f64> {
+        None
+    }
+}
+
 impl Context for MultiContext {
     fn get(&self, name: &str) -> Option<f64> {
         return self.vars.get(name).cloned();
@@ -34,7 +40,7 @@ impl MultiContext {
 }
 
 trait Eval: Derive + fmt::Display {
-    fn eval(&self, ctx: &dyn Context) -> f64;
+    fn eval(&self, ctx: &dyn Context) -> Value;
     fn boxed_clone(&self) -> Box<dyn Eval>;
 }
 
@@ -75,9 +81,9 @@ impl Derive for Value {
 }
 
 impl Eval for Value {
-    fn eval(&self, ctx: &dyn Context) -> f64 {
+    fn eval(&self, ctx: &dyn Context) -> Value {
         match self {
-            Self::Const(c) => *c,
+            Self::Const(c) => self.clone(),
             Self::Eval(e) => e.eval(ctx),
         }
     }
@@ -86,13 +92,26 @@ impl Eval for Value {
     }
 }
 
+impl Value {
+    fn result(&self) -> Option<f64> {
+        match self {
+            Self::Const(c) => Some(*c),
+            _ => None,
+        }
+    }
+}
+
 #[derive(Clone, Display)]
 #[display(fmt = "`{}`", _0)]
 struct Var(String);
 
 impl Eval for Var {
-    fn eval(&self, ctx: &dyn Context) -> f64 {
-        ctx.get(&self.0).unwrap()
+    fn eval(&self, ctx: &dyn Context) -> Value {
+        if let Some(c) = ctx.get(&self.0) {
+            Value::Const(c)
+        } else {
+            self.clone().into()
+        }
     }
     fn boxed_clone(&self) -> Box<dyn Eval> {
         Box::new(self.clone())
@@ -138,15 +157,36 @@ enum Op {
 }
 
 impl Eval for Op {
-    fn eval(&self, ctx: &dyn Context) -> f64 {
+    fn eval(&self, ctx: &dyn Context) -> Value {
         match self {
-            Self::Mul(a, b) => a.eval(ctx) * b.eval(ctx),
-            Self::Div(a, b) => a.eval(ctx) / b.eval(ctx),
-            Self::Add(a, b) => a.eval(ctx) + b.eval(ctx),
-            Self::Sub(a, b) => a.eval(ctx) - b.eval(ctx),
-            Self::Pow(a, b) => a.eval(ctx).powf(b.eval(ctx)),
-            Self::Ln(x) => x.eval(ctx).ln(),
-            Self::Exp(x) => x.eval(ctx).exp(),
+            Self::Mul(a, b) => match (a.eval(ctx), b.eval(ctx)) {
+                (Value::Const(a), Value::Const(b)) => Value::Const(a * b),
+                (a, b) => Self::mul(a, b).into(),
+            },
+            Self::Div(a, b) => match (a.eval(ctx), b.eval(ctx)) {
+                (Value::Const(a), Value::Const(b)) => Value::Const(a / b),
+                (a, b) => Self::div(a, b).into(),
+            },
+            Self::Add(a, b) => match (a.eval(ctx), b.eval(ctx)) {
+                (Value::Const(a), Value::Const(b)) => Value::Const(a + b),
+                (a, b) => Self::add(a, b).into(),
+            },
+            Self::Sub(a, b) => match (a.eval(ctx), b.eval(ctx)) {
+                (Value::Const(a), Value::Const(b)) => Value::Const(a - b),
+                (a, b) => Self::sub(a, b).into(),
+            },
+            Self::Pow(a, b) => match (a.eval(ctx), b.eval(ctx)) {
+                (Value::Const(a), Value::Const(b)) => Value::Const(a.powf(b)),
+                (a, b) => Self::pow(a, b).into(),
+            },
+            Self::Ln(x) => match x.eval(ctx) {
+                Value::Const(x) => Value::Const(x.ln()),
+                x => Self::ln(x).into(),
+            },
+            Self::Exp(x) => match x.eval(ctx) {
+                Value::Const(x) => Value::Const(x.exp()),
+                x => Self::exp(x).into(),
+            },
         }
     }
     fn boxed_clone(&self) -> Box<dyn Eval> {
@@ -214,12 +254,28 @@ impl Into<Value> for Op {
     }
 }
 
-fn newton_raphson<'a>(eq: &'a dyn Eval, x0: f64, precision: i32) -> impl Iterator<Item = f64> + 'a {
+fn take_while_unprecsise<'a>(
+    precision: i32,
+    it: impl Iterator<Item = f64> + 'a,
+) -> impl Iterator<Item = f64> + 'a {
+    let mut prev: Option<f64> = None;
+    it.filter(move |v| {
+        let prd = prev
+            .map(|prev| {
+                let d = dbg!((prev - v).abs());
+                d != 0.0 && d > dbg!(10.0f64.powi(-1 * precision))
+            })
+            .unwrap_or(true);
+        prev = Some(*v);
+        prd && false
+    })
+}
+
+fn newton_raphson<'a>(eq: &'a dyn Eval, x0: f64) -> impl Iterator<Item = f64> + 'a {
     //xp - f(x)/f'(x)
     let d = eq.derive();
     let eq = eq.clone();
     let mut i = 0;
-    let mut same_counter = 0usize;
     successors(Some(x0), move |xp: &f64| -> Option<f64> {
         let ctx = xp;
         let calc = Op::Sub(
@@ -228,16 +284,16 @@ fn newton_raphson<'a>(eq: &'a dyn Eval, x0: f64, precision: i32) -> impl Iterato
         );
         println!("( {}.) {} -> {}\n", &i, &calc, &xp);
         i += 1;
-        let x = calc.eval(ctx);
-        let equal = (x - xp).abs() < (10.0f64).powi(-1 * precision as i32);
-        if equal {
-            dbg!(("Reached precision after ", i));
+        let x = calc.eval(ctx).result().unwrap();
+        Some(x)
+    })
+    .take(10usize.pow(4))
+    .scan(None, |state: &mut Option<f64>, val| match state {
+        Some(pval) if pval.to_bits() == val.to_bits() => None,
+        _ => {
+            *state = Some(val);
+            Some(val)
         }
-        if same_counter > 3 {
-            dbg!(("Aborted after", i));
-        }
-        same_counter = (same_counter + equal as usize) * (equal as usize);
-        Some(x).filter(|_| !equal && same_counter < 3 && !x.is_nan())
     })
 }
 
@@ -247,7 +303,7 @@ fn n_root(number: f64, n: f64) -> Option<f64> {
         Value::Const(number),
     )
     .into();
-    newton_raphson(&eq, 1.0, 10).last()
+    take_while_unprecsise(1, newton_raphson(&eq, 1.0)).last()
 }
 
 fn main() {
@@ -267,11 +323,22 @@ fn main() {
         Value::Const(9.0),
     )
     .into();
+    println!("{}", eq.eval(&ctx));
     fn pow_to_x(b: f64) -> Value {
         Op::Pow(Value::Const(b), Var::val("x")).into()
     }
-    let eq: Value = Op::Sub(Op::Add(pow_to_x(4.0), pow_to_x(6.0)).into(), pow_to_x(9.0)).into();
+    let eq: Value = Op::sub(
+        Op::add(pow_to_x(4.0), pow_to_x(6.0)),
+        Op::pow(Op::add(5.0, 4.0), Op::mul(Var::val("x"), 1.0)),
+    )
+    .into();
     let res = n_root(9.4, 2.0);
-    let res = newton_raphson(&eq, 1.0, 8).last();
-    println!("1.0 - {}/{} ==> {}", &eq, "", res.unwrap());
+    //let res = newton_raphson(&eq, 1.0).last();
+    println!(
+        "{}\n1.0 - {}/{} ==> {}",
+        &eq,
+        &eq.eval(&()),
+        "",
+        res.unwrap()
+    );
 }