Tinker: a programming by Demonstration System for Beginning Programmers by Henry Lieberman Media Laboratory Massachusetts Institute of Technology


Figure 7: The obstacle is removed



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Figure 7: The obstacle is removed




We complete the definition by moving the unobstructed Block-X to the To block, Block-Y.


Figure 8: The end of the definition of the obstacle case









Distinguishing Between Multiple Examples For Stack

The situation is now that Tinker has two definitions, one for the simple case, another for the case. But as yet, Tinker does not know how to choose between the cases when it will encounter an example in the future. In such a situation, Tinker asks for the user's help to define, by example, a predicate that will make a decision as to which of the two definitions to use. This will generate a conditional procedure.

Tinker displays two Snapshot Windows, each displaying one of the cases, and asks the user to define an expression that will separate the cases. Each evaluation step is displayed simultaneously in both windows. For the condition to be valid as a decision rule, it is constrained to evaluate to true in one of the cases and false in the other case.







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