From da47b6baa2962925003381f0fab5f5f8cdb9ef6e Mon Sep 17 00:00:00 2001
From: Shimun <shimun@shimun.net>
Date: Fri, 22 Nov 2019 15:46:01 +0100
Subject: [PATCH] Implemented Op::{Ln, Exp} added precsion arg to raphson

---
 src/main.rs | 67 ++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 48 insertions(+), 19 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 7f8fe9c..6c1966e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,16 +4,29 @@ use std::collections::HashMap;
 use std::fmt;
 use std::iter::successors;
 #[derive(Clone)]
-struct Context {
+struct MultiContext {
     vars: HashMap<String, f64>,
 }
 
-impl Context {
+trait Context {
+    fn get(&self, name: &str) -> Option<f64>;
+}
+
+/// Simple Context will return it's value for any variable name
+impl Context for f64 {
+    fn get(&self, name: &str) -> Option<f64> {
+        Some(*self)
+    }
+}
+
+impl Context for MultiContext {
     fn get(&self, name: &str) -> Option<f64> {
         return self.vars.get(name).cloned();
     }
+}
 
-    fn with(&self, name: String, value: f64) -> Context {
+impl MultiContext {
+    fn with(&self, name: String, value: f64) -> Self {
         let mut n = self.clone();
         n.vars.insert(name, value);
         n
@@ -21,7 +34,7 @@ impl Context {
 }
 
 trait Eval: Derive + fmt::Display {
-    fn eval(&self, ctx: &Context) -> f64;
+    fn eval(&self, ctx: &dyn Context) -> f64;
     fn boxed_clone(&self) -> Box<dyn Eval>;
 }
 
@@ -56,10 +69,10 @@ impl Derive for Value {
 }
 
 impl Eval for Value {
-    fn eval(&self, ctx: &Context) -> f64 {
+    fn eval(&self, ctx: &dyn Context) -> f64 {
         match self {
             Self::Const(c) => *c,
-            Self::Eval(e) => e.eval(&ctx),
+            Self::Eval(e) => e.eval(ctx),
         }
     }
     fn boxed_clone(&self) -> Box<dyn Eval> {
@@ -72,7 +85,7 @@ impl Eval for Value {
 struct Var(String);
 
 impl Eval for Var {
-    fn eval(&self, ctx: &Context) -> f64 {
+    fn eval(&self, ctx: &dyn Context) -> f64 {
         ctx.get(&self.0).unwrap()
     }
     fn boxed_clone(&self) -> Box<dyn Eval> {
@@ -112,16 +125,22 @@ enum Op {
     Sub(Value, Value),
     #[display(fmt = "{}**({})", _0, _1)]
     Pow(Value, Value),
+    #[display(fmt = "ln({})", _0)]
+    Ln(Value),
+    #[display(fmt = "exp({})", _0)]
+    Exp(Value),
 }
 
 impl Eval for Op {
-    fn eval(&self, ctx: &Context) -> f64 {
+    fn eval(&self, ctx: &dyn Context) -> f64 {
         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(),
         }
     }
     fn boxed_clone(&self) -> Box<dyn Eval> {
@@ -148,7 +167,7 @@ impl Derive for Op {
             Self::Sub(a, b) => Op::Sub(a.derive(), b.derive()),
             Self::Pow(a, b) => match b {
                 Value::Eval(e) => Op::Mul(
-                    unimplemented!("Ln(x)"),
+                    Op::Ln(a.clone()).into(),
                     Op::Pow(a.clone(), b.clone()).into(),
                 ),
                 b => Op::Pow(
@@ -156,6 +175,8 @@ impl Derive for Op {
                     Op::Sub(b.clone(), Value::Const(1.0)).into(),
                 ),
             },
+            Self::Ln(x) => Op::Div(Value::Const(1.0), x.clone()),
+            Self::Exp(x) => Op::Mul(x.derive(), Op::Exp(x.clone()).into()),
         }
         .into()
     }
@@ -167,22 +188,30 @@ impl Into<Value> for Op {
     }
 }
 
-fn newton_raphson<'a>(eq: &'a dyn Eval, x0: f64) -> impl Iterator<Item = f64> + 'a {
+fn newton_raphson<'a>(eq: &'a dyn Eval, x0: f64, precision: i32) -> 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 = Context {
-            vars: vec![("x".to_string(), *xp)].into_iter().collect(),
-        };
+        let ctx = xp;
         let calc = Op::Sub(
             Var::val("x"),
             Op::Div(Value::Eval(eq.boxed_clone()), d.clone()).into(),
         );
         println!("( {}.) {} -> {}\n", &i, &calc, &xp);
         i += 1;
-        Some(calc.eval(&ctx)).filter(|x| (x - xp).abs() > (10.0f64).powf(-8.0))
+        let x = calc.eval(ctx);
+        let equal = (x - xp).abs() < (10.0f64).powi(-1 * precision as i32);
+        if equal {
+            dbg!(("Reached precision after ", i));
+        }
+        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)
     })
 }
 
@@ -192,11 +221,11 @@ fn n_root(number: f64, n: f64) -> Option<f64> {
         Value::Const(number),
     )
     .into();
-    newton_raphson(&eq, 1.0).last()
+    newton_raphson(&eq, 1.0, 10).last()
 }
 
 fn main() {
-    let ctx = Context {
+    let ctx = MultiContext {
         vars: vec![("x".to_string(), 5.0)].into_iter().collect(),
     };
     let eq = Op::Sub(
@@ -216,7 +245,7 @@ fn main() {
         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 res = n_root(9.0, 2.0);
-    let res = newton_raphson(&eq, 1.0).last();
-    println!("1.0 - {}/{} ==> {}", &eq, eq.derive(), res.unwrap());
+    let res = n_root(9.0, 2.0);
+    let res = newton_raphson(&eq, 1.0, 10).last();
+    println!("1.0 - {}/{} ==> {}", &eq, "", res.unwrap());
 }