Creating and Editing a Regular Expression

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Creating a new Regular Expression

To create a new Regular Expression, look for the list of possible formal language types and click on Regular Expression.

You will see a split screen with a drawing area on the left and an editing area to the right.
The drawing area is not particularly useful here -- all of the action for regular expressions takes place in the editing area.

You can now build your new regular expression by typing into the provided box.

Testing a Regular Expression

You can "test" your RE by simulating its execution on an input string.

Below the main editing area for your FA, you can see the testing area:

  • Type any alphanumeric string into the "Input text:" box, and click on Test.

    You will be told whether the regular expression accepts that string or rejects it.

    • Unlike with finite automata, there is no option for single-stepping regular expressions through the input string.