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Location: Chapter 21, solution to Problems 3 and 4

Note: additional solutions due to bird expressions equivalent to those given in the text.

Problem 3 (c)

Besides the solution L(LL)(L(LL)), the following is also valid:


Problem 4

Besides the solution L(BKM)(L(BKM)), the following is also valid:


Short explanation

According to the first method illustrated in the Chapter, any bird A is a good solution as long as it is built according to

A = LA_1(LA_1)\;,

where all that is needed from A_1, in turn, is that it satisfies a problem-specific condition. Hence, if more than one bird A_1 is found for a certain Problem, it automatically follows that there are more than one solution for the Problem.

For Problem 3 (c), two expressions for A_1 can be found:


and likewise for Problem 4: