fix tabulation and gaps in expression.rb

lib/ruby_algebra/expression.rb

@@ -69,6 +69,7 @@ module RubyAlgebra
     def type
       :sub
     end
+
     def diff(v)
       Subtraction.new(@lhs.diff(v), @rhs.diff(v))
     end
@@ -114,13 +115,14 @@ module RubyAlgebra
     def op_assoc_type
       :left
     end
+
     def diff(v)
-    u_prime = @lhs.diff(v)
-    v_prime = @rhs.diff(v)
-    term1 = Multiplication.new(u_prime, @rhs)
-    term2 = Multiplication.new(@lhs, v_prime)
-    Addition.new(term1, term2)
-  end
+      u_prime = @lhs.diff(v)
+      v_prime = @rhs.diff(v)
+      term1 = Multiplication.new(u_prime, @rhs)
+      term2 = Multiplication.new(@lhs, v_prime)
+      Addition.new(term1, term2)
+    end
   end
 
   class Division < Multiplication
@@ -176,6 +178,7 @@ module RubyAlgebra
     def op_assoc_type
       :right
     end
+
     def diff(v)
       unless @exponent.is_a?(Constant)
         raise NotImplementedError, "Дифференцирование степени с неконстантным показателем не реализовано"
@@ -244,6 +247,7 @@ module RubyAlgebra
     def single_letter?
       @is_single_letter
     end
+
     def diff(v)
       @symbol == v ? Constant.new(1) : Constant.new(0)
     end