title: Jenkins DSL workflow for performing subtraction
body: <p>I have written a jenkins script where i want build no and previous build no.For that i am performing a subtraction operation.
  i want to perform a subtraction between two variables in jenkins  DSL script.</p>
  
  <p>But i am not able to subtract.Ex i want to perform a=b-1 ....</p>
  
  <p>the result what i am getting is always value of b.it does not perform subtraction.</p>
  
  <p>It just assigns value of b to a.</p>
  
  <p>Below is want i want :</p>
  
  <p>build_num = "3"</p>
  
  <p>pre_build_num = build_num-"1"</p>
  
  <p>and result what i want should be pre_build_num = "2".</p>
  
  <p>But i am getting pre_build_num = "3".</p>
  
  <p>any help?</p>