primitive recursive predicate

primitive recursive predicates are primitive recursive functions whose range is , 0 and 1 being substitutes for true and false.
[cite:;taken from @computability_davis_1994 chapter 3.5 primitive recursive functions]
the function is defined as
is primitive recursive since
or we can simply write the recursion equations:
[cite:;taken from @computability_davis_1994 chapter 3.5 primitive recursive functions]
the predicate is defined as 1 if the values of and are the same and 0 otherwise. thus we wish to show that the function
is primitive recursive. this follows immediately from the equation
[cite:;taken from @computability_davis_1994 chapter 3.5 primitive recursive functions]
this predicate is simply the primitive recursive function .
[cite:;taken from @computability_davis_1994 chapter 3.5 primitive recursive functions]
let be a PRC class. if are predicates that belong to , then so are , and .
[cite:;taken from @computability_davis_1994 theorem 5.1]
we can write
or more simply
[cite:;taken from @computability_davis_1994 chapter 3.5 primitive recursive functions]
let be a PRC class. let the functions and the predicate belong to . let
then belongs to .
[cite:;taken from @computability_davis_1994 theorem 5.4]
let be a PRC class, let -ary functions and predicates belong to , and let
for all and all . if
then also belongs to .
[cite:;taken from @computability_davis_1994 corollary 5.5]
if the predicate belongs to some PRC class , then so do the predicates
this is directly related to unbounded_search_operator.html.
[cite:;taken from @computability_davis_1994 theorem 6.3]
is the predicate "y is a divisor of ." for example.
is true, while
is false.
the predicate is primitive recursive since
[cite:;taken from @computability_davis_1994 chapter 3.6 iterated operations and bounded quantifiers]
the predicate " is a prime" is primitive recursive since
(a number is a prime if it is greater than 1 and it has no divisors other than 1 and itself.)
[cite:;taken from @computability_davis_1994 chapter 3.6 iterated operations and bounded quantifiers]