Disappointing? You are the one coming to me expecting an example-oracle that produces them on demand.<p>E.g.<p>Computation &#x2F; representation:<p><pre><code>    2 + 2
</code></pre>
Graph<p><pre><code>       [+]

      &#x2F;   \

    [2]    [2]
</code></pre>
There is a way to produce the graph from the computation &#x2F; representation and vice versa. There is a way to do that for every possible computation &#x2F; representation and every possible graph (though, not necessarily with every pair).<p>This could be described as a compiler or compiler-like. There are many interesting things to do with them, but in this example all that is needed to consider is the construction of an Abstract Syntax <i>Tree</i> from a string and an in-order tree walker that emits the contents of the nodes to an output string.