From 1c6c2b24ffecd8adfe9bd9782e28a7b640637351 Mon Sep 17 00:00:00 2001
From: Chernykh Aleksandr <dernet4@gmail.com>
Date: Mon, 23 Mar 2026 17:15:42 +0300
Subject: [PATCH] evaluate

---
 lib/ruby_algebra/expression.rb | 64 ++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/lib/ruby_algebra/expression.rb b/lib/ruby_algebra/expression.rb
index 0914810..1871ccd 100644
--- a/lib/ruby_algebra/expression.rb
+++ b/lib/ruby_algebra/expression.rb
@@ -20,6 +20,12 @@ module RubyAlgebra
     def diff(v)
       raise NotImplementedError, "#{self.class}#diff not implemented"
     end
+    def evaluate
+      raise NotImplementedError, "#{self.class}#evaluate not implemented"
+    end
+    def constant?
+      raise NotImplementedError, "#{self.class}#constant? not implemented"
+    end
   end
 
   class Addition < Expression
@@ -59,6 +65,15 @@ module RubyAlgebra
     def diff(v)
       Addition.new(@lhs.diff(v), @rhs.diff(v))
     end
+    def evaluate
+      lhs_val = @lhs.evaluate
+      rhs_val = @rhs.evaluate
+      return nil if lhs_val.nil? || rhs_val.nil?
+      lhs_val + rhs_val
+    end
+    def constant?
+      @lhs.constant? && @rhs.constant?
+    end
   end
 
   class Subtraction < Addition
@@ -79,6 +94,15 @@ module RubyAlgebra
     def diff(v)
       Subtraction.new(@lhs.diff(v), @rhs.diff(v))
     end
+    def evaluate
+      lhs_val = @lhs.evaluate
+      rhs_val = @rhs.evaluate
+      return nil if lhs_val.nil? || rhs_val.nil?
+      lhs_val - rhs_val
+    end
+    def constant?
+      @lhs.constant? && @rhs.constant?
+    end
   end
 
   class Multiplication < Expression
@@ -134,6 +158,15 @@ module RubyAlgebra
       term2 = Multiplication.new(@lhs, v_prime)
       Addition.new(term1, term2)
     end
+    def evaluate
+      lhs_val = @lhs.evaluate
+      rhs_val = @rhs.evaluate
+      return nil if lhs_val.nil? || rhs_val.nil?
+      lhs_val * rhs_val
+    end
+    def constant?
+      @lhs.constant? && @rhs.constant?
+    end
   end
 
   class Division < Multiplication
@@ -159,6 +192,16 @@ module RubyAlgebra
       denominator = Power.new(@rhs, Constant.new(2))
       Division.new(numerator, denominator)
     end
+    def evaluate
+      lhs_val = @lhs.evaluate
+      rhs_val = @rhs.evaluate
+      return nil if lhs_val.nil? || rhs_val.nil?
+      return nil if rhs_val == 0
+      lhs_val / rhs_val
+    end
+    def constant?
+      @lhs.constant? && @rhs.constant?
+    end
   end
 
   class Power < Expression
@@ -207,6 +250,15 @@ module RubyAlgebra
       coeff = Constant.new(n)
       Multiplication.new(coeff, Multiplication.new(new_power, base_diff))
     end
+    def evaluate
+      base_val = @base.evaluate
+      exp_val = @exponent.evaluate
+      return nil if base_val.nil? || exp_val.nil?
+      base_val ** exp_val
+    end
+    def constant?
+      @base.constant? && @exponent.constant?
+    end
   end
 
   class Constant < Expression
@@ -240,6 +292,12 @@ module RubyAlgebra
     def diff(v)
       Constant.new(0)
     end
+    def evaluate
+      @value
+    end
+    def constant?
+      true
+    end
   end
 
   class Variable < Expression
@@ -278,5 +336,11 @@ module RubyAlgebra
     def diff(v)
       @symbol == v ? Constant.new(1) : Constant.new(0)
     end
+    def evaluate
+      nil
+    end
+    def constant?
+      false
+    end
   end
 end