Determine the number c of elements in the list x that satisfy the predicate p.
my $c = grep { p($_) } @x;
c=count(p(x))
c := 0 for _, v := range x { if p(v) { c++ } }
func count[T any](x []T, p func(T) bool) int { c := 0 for _, v := range x { if p(v) { c++ } } return c }
let c = x.filter(p).length
import java.util.ArrayList; import java.util.Collections;
int c = Collections.frequency(x, p);
c := 0; for el in x do if p(el) then Inc(c);
c = sum(p(v) for v in x)
c = x.count{|el| p(el) }
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