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Regular Expression Parser

StateMachine for Regular Expression Parser

The Class RegularExpressionParser is defined with one attribute: bMatch.

A StateMachine is used to describe the regular expression (a|b)*abb

  • The transition triggers are specified as events a, b, x and reset
  • On entry to State4, bMatch is set to True; on exit from State4, bMatch is set to False
  • On entry to State5, bMatch is set to False
  • On self transition of State6, bMatch is set to False

Customize index.html and statemachineGUI.js

Make these changes to the generated files:

  • Create an HTML input field and an image to indicate the result
  • Create JavaScript as the field's oninput event handler
  • Create the function SetResult to toggle the pass/fail image
  • Create the function getEventStr, which will return 'a' on 'a' and 'b' on 'b', but will return 'x' on any other character
  • On initialize, broadcast 'reset'
  • On the broadcast event, request the runtime variable 'regxParser.bMatch'

In statemachineGUI.js, find the function onRuntimeValueResponse

  • In 'regxParser.bMatch', we will receive 'True' or 'False' and pass it into SetResult to update the image

The Complete Example

The example can be accessed from the 'Resources' page of the Sparx Systems website by clicking on this link:

Regular Expression Parser Simulation