Determine output language by output file extension

lib/propane/generator.rb

@@ -11,14 +11,26 @@ class Propane
         @log = StringIO.new
       end
       @classname = @grammar.classname || File.basename(output_file).sub(%r{[^a-zA-Z0-9].*}, "").capitalize
+      @language =
+        if output_file =~ /\.([a-z]+)$/
+          $1
+        else
+          "d"
+        end
       process_grammar!
     end
 
     def generate
-      erb = ERB.new(File.read(File.join(File.dirname(File.expand_path(__FILE__)), "../../assets/parser.d.erb")), trim_mode: "<>")
-      result = erb.result(binding.clone)
-      File.open(@output_file, "wb") do |fh|
-        fh.write(result)
+      extensions = [@language]
+      if @language == "c"
+        extensions += %w[h]
+      end
+      extensions.each do |extension|
+        erb = ERB.new(File.read(File.join(File.dirname(File.expand_path(__FILE__)), "../../assets/parser.#{extension}.erb")), trim_mode: "<>")
+        result = erb.result(binding.clone)
+        File.open(@output_file.sub(%r{\.[a-z]+$}, ".#{extension}"), "wb") do |fh|
+          fh.write(result)
+        end
       end
       @log.close
     end
@@ -191,7 +203,12 @@ class Propane
         end
         code = code.gsub(/\$(\d+)/) do |match|
           index = $1.to_i
-          "statevalues[$-1-n_states+#{index}].pvalue.v_#{rule.components[index - 1].ptypename}"
+          case @language
+          when "d"
+            "statevalues[$-1-n_states+#{index}].pvalue.v_#{rule.components[index - 1].ptypename}"
+          when "c"
+            "state_value_stack_index(statevalues, -1 - (int)n_states + #{index})->pvalue.v_#{rule.components[index - 1].ptypename}"
+          end
         end
       else
         code = code.gsub(/\$\$/) do |match|