anchor.diff:                  var viewModel = window.viewModel = {}
                   ;(function() {
                       this.view = ko.observable('js')
  -                    this.errors = ko.observable()
  +                    this.parserErrors = ko.observable()
  +                    this.compilerErrors = ko.observable()
                       this.ast = ko.observable()
                       this.compiledJs = ko.observable()
                       this.inputAngl = ko.observable('')
  
positive.code:                         try {
                              this.ast(angl.parse(this.inputAngl()))
                          } catch(e) {
                              this.errors(e.message)
                              return
                          }
                          try {
                              this.compiledJs(compiler(this.ast()))
                          } catch(e) {
                              this.errors(e.message)
                              return
                          }
                          this.errors(undefined)
                      }, this).extend({throttle: 500})
                  }).apply(viewModel)
  
  
negative.code:                 label Javascript
  
              #output.fill-container.container
                  // ko if: view() == 'js'
                  // ko ifnot: compilerErrors
                  code#compiledCode.scroll-box
                      pre(data-bind="text: compiledJs")
                  // /ko
                  // ko if: compilerErrors
                  pre#error.scroll-box(data-bind="text: compilerErrors")
                  // /ko
                  // /ko
                  // ko if: view() == 'ast'
                  // ko ifnot: parserErrors
                  code#compiledCode.scroll-box
                      pre(data-bind="text: JSON.stringify(ast(), null, '    ')")
                  // /ko
                  // ko if: parserErrors
                  pre#error.scroll-box(data-bind="text: parserErrors")
                  // /ko
                  // /ko
  