initiates a dialog for every expression used in the evaluation of expr.
initiates a dialog only for expressions which match form.
initiates dialogs only for expressions whose evaluations use transformation rules associated with the symbol s.
Basic Examples (1)
Trace evaluation of an expression, entering a Dialog whenever addition is encountered:
In the dialog you can look at the evaluation stack:
This returns from the first dialog:
Another dialog has started:
In the dialog, you can check evaluations to see if they come out as you expect:
Return from the second dialog. Since there are no more additions, the evaluation will finish:
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