float类型得分计算最终得分时精度损失

app/controllers/student_work_controller.rb

@@ -1,6 +1,7 @@
 class StudentWorkController < ApplicationController
   layout "base_courses"
   include StudentWorkHelper
+  require 'bigdecimal'
   before_filter :find_homework, :only => [:new, :index, :create]
   before_filter :find_work, :only => [:edit, :update, :show, :destroy, :add_score, :praise_student_work]
   before_filter :member_of_course, :only => [:index, :new, :create, :show, :add_score, :praise_student_work]
@@ -150,7 +151,10 @@ class StudentWorkController < ApplicationController
             if @work.student_score.nil?
               @work.final_score = @work.teaching_asistant_score
             else
-              @work.final_score = format("%.2f",@work.teaching_asistant_score * @homework.homework_detail_manual.ta_proportion + @work.student_score * (1 - @homework.homework_detail_manual.ta_proportion))
+              final_ta_score = BigDecimal.new("#{@work.teaching_asistant_score}") * BigDecimal.new("#{@homework.homework_detail_manual.ta_proportion}")
+              final_s_score = BigDecimal.new("#{@work.student_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{@homework.homework_detail_manual.ta_proportion}"))
+              final_score = final_ta_score + final_s_score
+              @work.final_score = format("%.2f",final_score.to_f)
             end
           end
         when 3 #学生评分 学生评分显示平均分
@@ -159,7 +163,10 @@ class StudentWorkController < ApplicationController
             if @work.teaching_asistant_score.nil?
               @work.final_score = @work.student_score
             else
-              @work.final_score = format("%.2f",@work.teaching_asistant_score * @homework.homework_detail_manual.ta_proportion + @work.student_score * (1 - @homework.homework_detail_manual.ta_proportion))
+              final_ta_score = BigDecimal.new("#{@work.teaching_asistant_score}") * BigDecimal.new("#{@homework.homework_detail_manual.ta_proportion}")
+              final_s_score = BigDecimal.new("#{@work.student_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{@homework.homework_detail_manual.ta_proportion}"))
+              final_score = final_ta_score + final_s_score
+              @work.final_score = format("%.2f",final_score.to_f)
             end
           end
       end