Evaluate definition/indentifier

lib/chervil.rb

 require 'chervil/ast'
+require 'chervil/env'
 require 'chervil/interpreter'
 require 'chervil/lexer'
 require 'chervil/parser'

lib/chervil/ast/definition.rb

     def ==(other)
       @name == other.name && @value == other.value
     end
+
+    def evaluate(env)
+      env.set(@name.name, @value)
+    end
   end
 end

lib/chervil/ast/identifier.rb

     def ==(other)
       @name == other.name
     end
+
+    def evaluate(env)
+      env.get(@name)
+    end
   end
 end

lib/chervil/interpreter.rb

     end
 
     def interpret
-      @tree.map(&:evaluate)
+      env = Env.new
+      @tree.map { |node| node.evaluate(env) }
     end
   end
 end

spec/ast/definition_spec.rb

+module Chervil
+  RSpec.describe AST::Definition do
+    it 'evaluates' do
+      env = Env.new
+      AST::Definition.new(
+        AST::Identifier.new("x"),
+        AST::Number.new(5.0)
+      ).evaluate(env)
+      expect(env.get("x")).to eq(AST::Number.new(5.0))
+    end
+  end
+end

spec/ast/identifier_spec.rb

+module Chervil
+  RSpec.describe AST::Identifier do
+    it 'evaluates' do
+      env = Env.new
+      identifier = AST::Identifier.new("x")
+      value = AST::Number.new(5.0)
+      definition = AST::Definition.new(identifier, value)
+      definition.evaluate(env)
+      expect(identifier.evaluate(env)).to eq(value)
+    end
+  end
+end