A parse utility for PEG parsers, which includes:

1. Grammar tasks
2. PEG Playground
3. Abstract syntax tree of input text

Grammar tasks

Grammar tasks are inspired by the Caterpillar logic game.

In each task, a user has to construct a grammar that would be similar to a task grammar (which is hidden) by testing different inputs. For each input the program says whether it is valid for the task grammar or not. To make it easier, each task already has 5 valid and invalid inputs.

Example

Suppose we are given a task, and we know that following inputs are valid:

        01010101
        101
        11100001
        110101011
        00110

And following are invalid:

        0
        1
        1111
        00
        0000

We can assume that input is valid if it contains both 1 and 0. Let's create a grammar and test it:

We get: WA: 101. It is wrong because we need even number of ones. Therefore, this grammar should work: