gtest/samples/prime_tables.h
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30 // Author: wan@google.com (Zhanyong Wan)
31 // Author: vladl@google.com (Vlad Losev)
32 
33 // This provides interface PrimeTable that determines whether a number is a
34 // prime and determines a next prime number. This interface is used
35 // in Google Test samples demonstrating use of parameterized tests.
36 
37 #ifndef GTEST_SAMPLES_PRIME_TABLES_H_
38 #define GTEST_SAMPLES_PRIME_TABLES_H_
39 
40 #include <algorithm>
41 
42 // The prime table interface.
43 class PrimeTable
44 {
45 public:
46  virtual ~PrimeTable() {}
47 
48  // Returns true iff n is a prime number.
49  virtual bool IsPrime(int n) const = 0;
50 
51  // Returns the smallest prime number greater than p; or returns -1
52  // if the next prime is beyond the capacity of the table.
53  virtual int GetNextPrime(int p) const = 0;
54 };
55 
56 // Implementation #1 calculates the primes on-the-fly.
57 class OnTheFlyPrimeTable : public PrimeTable
58 {
59 public:
60  virtual bool IsPrime(int n) const
61  {
62  if (n <= 1) { return false; }
63 
64  for (int i = 2; i * i <= n; i++)
65  {
66  // n is divisible by an integer other than 1 and itself.
67  if ((n % i) == 0) { return false; }
68  }
69 
70  return true;
71  }
72 
73  virtual int GetNextPrime(int p) const
74  {
75  for (int n = p + 1; n > 0; n++)
76  {
77  if (IsPrime(n)) { return n; }
78  }
79 
80  return -1;
81  }
82 };
83 
84 // Implementation #2 pre-calculates the primes and stores the result
85 // in an array.
87 {
88 public:
89  // 'max' specifies the maximum number the prime table holds.
90  explicit PreCalculatedPrimeTable(int max)
91  : is_prime_size_(max + 1), is_prime_(new bool[max + 1])
92  {
93  CalculatePrimesUpTo(max);
94  }
95  virtual ~PreCalculatedPrimeTable() { delete[] is_prime_; }
96 
97  virtual bool IsPrime(int n) const
98  {
99  return 0 <= n && n < is_prime_size_ && is_prime_[n];
100  }
101 
102  virtual int GetNextPrime(int p) const
103  {
104  for (int n = p + 1; n < is_prime_size_; n++)
105  {
106  if (is_prime_[n]) { return n; }
107  }
108 
109  return -1;
110  }
111 
112 private:
113  void CalculatePrimesUpTo(int max)
114  {
115  ::std::fill(is_prime_, is_prime_ + is_prime_size_, true);
116  is_prime_[0] = is_prime_[1] = false;
117 
118  for (int i = 2; i <= max; i++)
119  {
120  if (!is_prime_[i]) { continue; }
121 
122  // Marks all multiples of i (except i itself) as non-prime.
123  for (int j = 2 * i; j <= max; j += i)
124  {
125  is_prime_[j] = false;
126  }
127  }
128  }
129 
130  const int is_prime_size_;
131  bool * const is_prime_;
132 
133  // Disables compiler warning "assignment operator could not be generated."
134  void operator=(const PreCalculatedPrimeTable & rhs);
135 };
136 
137 #endif // GTEST_SAMPLES_PRIME_TABLES_H_
virtual int GetNextPrime(int p) const
virtual int GetNextPrime(int p) const
virtual bool IsPrime(int n) const =0
virtual bool IsPrime(int n) const
virtual bool IsPrime(int n) const
virtual int GetNextPrime(int p) const =0


ros_opcua_impl_freeopcua
Author(s): Denis Štogl
autogenerated on Tue Jan 19 2021 03:12:07