[e12e]

Ah, from tfa:

> How Preview Execution Works

> Under the hood, preview execution works by using Scheme environments.

> When code is highlighted, Toski duplicates the current environment and executes the code. Then, when the cursor is moved or the code is de-selected, Toski removes the new environment, returning the instance to the previous state.

Which makes sense - but it would be cool if it automagically mocked all external calls... ;)

[chii]

or, just showed you a call graph, with symbolic values - e.g., instead of printing 'hello world', it would show a box, highlighting the argument to the 'display' function , and showed how that argument value is propagated through the rest of the code. If i clicked on the highlighted argument, and started typing, i should be able to see how my changes affect the flow and what the output might be.