### Error in Sample Solution of Exercise 5.2

Verfasst:

**6. Dez 2017 14:45**hello,

Exercise 5.2 a) requires the abstract interpretation functions for assignments to be optimal.

I think the given functions for assignments S1 and S2 in the sample solution are not optimal.

For example for f_S1, there is a more informative function f'_S1 (f_S1 is not at least as informative as f'_S1)

which is defined like f_S1,

but f'_S1(l)(y) = none if l(y) = none.

f'_S1 is also correct with respect to the representation function beta:

Since

beta(sigma)(y) [= l(y) = none

cannot be satisfied (none is not in the image of beta), we do not need to consider whether

pos = beta(sigma_res)(y) [= f'_S1(l)(y) = none

is satisfied or not.

Best regards,

Alexander

Exercise 5.2 a) requires the abstract interpretation functions for assignments to be optimal.

I think the given functions for assignments S1 and S2 in the sample solution are not optimal.

For example for f_S1, there is a more informative function f'_S1 (f_S1 is not at least as informative as f'_S1)

which is defined like f_S1,

but f'_S1(l)(y) = none if l(y) = none.

f'_S1 is also correct with respect to the representation function beta:

Since

beta(sigma)(y) [= l(y) = none

cannot be satisfied (none is not in the image of beta), we do not need to consider whether

pos = beta(sigma_res)(y) [= f'_S1(l)(y) = none

is satisfied or not.

Best regards,

Alexander