BetaRedex2.init() BetaRedex2.expression BetaRedex2.answer BetaRedex2.hint5

The following λ expression contains exactly one β-redex:

expression

True or False? An α-conversion is required when performing one full execution of the substitution algorithm needed to perform the first step (or β-reduction) in the evaluation of this redex.

correctAnswer
  • True
  • False

Once you have identified the β-redex in the expression given above, write down the substitution that is needed to reduce it, that is, replace the question marks in subst( ?, ?, ?).

Once you have identified the substitution that must take place, determine which (sub-)case of the substitution algorithm applies.

Identifying the applicable (sub-)case of the substitution algorithm immediately gives you the answer to this problem, since α-conversions are only required in one sub-case.

Watch out! The single β-reduction that you are asked to think about translates into a call to the substitute algorithm, which can make several recursive calls as the substitution proceeds through the whole body of the λ abstraction

hint5