Calculator

<%= label_tag :input, "Input", class: 'control-label' %> <%= text_field_tag :input, nil, class: 'form-control', autofocus: true %>
<%= label_tag :output_unit, "Output Unit", class: 'control-label' %> <%= text_field_tag :output_unit, nil, class: 'form-control' %>
<%= label_tag :output, "Output", class: 'control-label' %> <%= text_field_tag :output, nil, class: 'form-control', readonly: true %>