title: How to add jenkinsfile parameter values
body: <p>In my jenkinsfile, I have following params and would like to create a env variable that sums up these two params. How to do this?</p>
  
  <pre><code>parameters {
  string(name: 'log_act_instances', defaultValue: '1')
  string(name: 'log_arb_instances', defaultValue: '1')
  }
  
  environment {
  log_instances = log_act_instances+log_arb_instances (Value should be 2 for log_instances)
  }
  </code></pre>