3.7. References 77
the propositional operators, variables and quantifiers, you may define predicates
using addition, multiplication, and equality symbols, and nonnegative integercon-
stants( 0 , 1 ,... ), but noexponentiation(likexy). For example, the predicate “n is
an even number” could be defined by either of the following formulas:
9 m: .2mDn/; 9 m: .mCmDn/:(a)mis a divisor ofn.(b)nis a prime number.(c)nis a power of a prime.Problem 3.30.
Translate the following sentence into a predicate formula:
There is a student who has e-mailed at most two other people in the
class, besides possibly himself.The domain of discourse should be the set of students in the class; in addition,
the only predicates that you may use are
equality, and E.x;y/, meaning that “xhas sent e-mail toy.”Problem 3.31.
Translate the following sentence into a predicate formula:
There is a student who has emailed exactly two other people in the
class, besides possibly herself.The domain of discourse should be the set of students in the class; in addition,
the only predicates that you may use are
equality, and E.x;y/, meaning that “xhas sent e-mail toy.”