diff --git a/minlisp.rb b/minlisp.rb
index 423ccac..338ba9e 100644
--- a/minlisp.rb
+++ b/minlisp.rb
@@ -44,17 +44,16 @@ end
 
 def atom(token)
   # Analyse numbers and symbols
-  isInteger = ->(atom) { atom.match?(/^-?\d+$/) }
-  isFloat   = ->(atom) { atom.match?(/^(-?\d+)(\.\d+)?$/) }
-  return Integer token if isInteger.call token
-  return Float   token if isFloat.call   token
+  is_integer = ->(atom) { atom.match?(/^-?\d+$/) }
+  is_float   = ->(atom) { atom.match?(/^(-?\d+)(\.\d+)?$/) }
+  return Integer token if is_integer.call token
+  return Float   token if is_float.call   token
 
   token.to_sym
 end
 
 # p parse '(def 1 2 (c 3.3 (r f r) e))'
 
-
 ##### Environments
 
 def generate_env