2 files changed, 47 insertions, 35 deletions

diff --git a/lib/elixir_math_parser.ex b/lib/elixir_math_parser.ex
index 1f147aa..91f67f9 100644
--- a/lib/elixir_math_parser.ex
+++ b/lib/elixir_math_parser.ex
@@ -4,46 +4,58 @@ defmodule ElixirMathParser do
   """
 
   defp reduce_to_value({:int, _line, value}, _state) do
-    value
+    {:ok, value}
+  end
+
+  defp reduce_to_value({:atom, _line, atom}, state) do
+    if !Map.has_key?(state, atom) do
+      {:error, "value not found for " <> to_string(atom)}
+    else
+      {:ok, state[atom]}
+    end
   end
 
   defp reduce_to_value({:add_op, lhs, rhs}, state) do
-    reduce_to_value(lhs, state) + reduce_to_value(rhs, state)
+    {:ok, op1} = reduce_to_value(lhs, state)
+    {:ok, op2} = reduce_to_value(rhs, state)
+    {:ok, op1 + op2}
   end
 
   defp reduce_to_value({:sub_op, lhs, rhs}, state) do
-    reduce_to_value(lhs, state) - reduce_to_value(rhs, state)
+    {:ok, op1} = reduce_to_value(lhs, state)
+    {:ok, op2} = reduce_to_value(rhs, state)
+    {:ok, op1 - op2}
   end
 
   defp reduce_to_value({:mul_op, lhs, rhs}, state) do
-    reduce_to_value(lhs, state) * reduce_to_value(rhs, state)
+    {:ok, op1} = reduce_to_value(lhs, state)
+    {:ok, op2} = reduce_to_value(rhs, state)
+    {:ok, op1 / op2}
   end
 
   defp reduce_to_value({:div_op, lhs, rhs}, state) do
-    reduce_to_value(lhs, state) / reduce_to_value(rhs, state)
+    {:ok, op1} = reduce_to_value(lhs, state)
+    {:ok, op2} = reduce_to_value(rhs, state)
+    {:ok, op1 / op2}
   end
 
-  defp reduce_to_value({:atom, _line, atom}, state) do
-    state[atom]
-  end
-  
   defp evaluate_tree([{:assign, {:atom, _line, lhs}, rhs} | tail], state) do
-    rhs_value = reduce_to_value(rhs, state)
+    {:ok, rhs_value} = reduce_to_value(rhs, state)
     evaluate_tree(tail, Map.merge(state, %{lhs => rhs_value}))
   end
 
-   defp evaluate_tree([], state) do
-     state
-   end
+  defp evaluate_tree([], state) do
+    state
+  end
 
-   def process_tree(tree) do
-     evaluate_tree(tree, %{})
-   end
+  def process_tree(tree) do
+    evaluate_tree(tree, %{})
+  end
 
-   def parse_file(filename) do
-     text = File.read!(filename)
-     {:ok, tokens, _line} = :elixir_math_parser_lexer.string(String.to_charlist(text))
-     {:ok, tree} = :elixir_math_parser.parse(tokens)
-     process_tree(tree)        
-   end
+  def parse_file(filename) do
+    text = File.read!(filename)
+    {:ok, tokens, _line} = :elixir_math_parser_lexer.string(String.to_charlist(text))
+    {:ok, tree} = :elixir_math_parser.parse(tokens)
+    process_tree(tree)
+  end
 end
diff --git a/lib/main.ex b/lib/main.ex
index ca73cb5..f1f0a20 100644
--- a/lib/main.ex
+++ b/lib/main.ex
@@ -1,28 +1,28 @@
 defmodule ElixirMathParser.Main do
-   def process_parse({:error, result}) do
-    IO.puts "\nParse error"
-    IO.inspect result
+  def process_parse({:error, result}) do
+    IO.puts("\nParse error")
+    IO.inspect(result)
   end
 
   def process_parse({:ok, tree}) do
-    IO.puts "\nParse tree"
-    IO.inspect tree, pretty: true
+    IO.puts("\nParse tree")
+    IO.inspect(tree, pretty: true)
     state = ElixirMathParser.process_tree(tree)
-    IO.puts "\nFinal state"
-    IO.inspect state, pretty: true
+    IO.puts("\nFinal state")
+    IO.inspect(state, pretty: true)
   end
-  
+
   def main(args) do
     filename = Enum.fetch!(args, 0)
 
-    IO.puts "Parsing #{filename}"
+    IO.puts("Parsing #{filename}")
     text = File.read!(filename)
 
     {:ok, tokens, line} = :elixir_math_parser_lexer.string(String.to_charlist(text))
-    IO.puts "Parsed #{filename}, stopped at line #{line}"
-    IO.puts "\nTokens:"
-    IO.inspect tokens, pretty: true
+    IO.puts("Parsed #{filename}, stopped at line #{line}")
+    IO.puts("\nTokens:")
+    IO.inspect(tokens, pretty: true)
 
     process_parse(:elixir_math_parser.parse(tokens))
-  end 
+  end
 end