Assertions
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#undef NDEBUG #include "Utils.hpp" #include <fmt/format.h> #include <iostream> #include <string> using namespace std; static double const TEST_BASE = 0.9; double exponentiation(double base, int powerArg) noexcept { precondition(powerArg >= 0, "powerArg >= 0"); int power = powerArg; double result = 1; while (power > 0) { result *= base; --power; } return result; } int main(int argc, char **argv) { for (int p = 10; p >= -1; --p) { cout << fmt::format("{0:f} ^ {1:d} = {2:f}", TEST_BASE, p, exponentiation(TEST_BASE, p)) << endl; } return 0; }
Output
$ g++ -std=c++17 Assertions1.cpp -o Assertions1 -lfmt
$ ./Assertions1
0.900000 ^ 10 = 0.348678
0.900000 ^ 9 = 0.387420
0.900000 ^ 8 = 0.430467
0.900000 ^ 7 = 0.478297
0.900000 ^ 6 = 0.531441
0.900000 ^ 5 = 0.590490
0.900000 ^ 4 = 0.656100
0.900000 ^ 3 = 0.729000
0.900000 ^ 2 = 0.810000
0.900000 ^ 1 = 0.900000
0.900000 ^ 0 = 1.000000
Precondition failed: powerArg >= 0, File: Assertions1.cpp Line: 13.
#undef NDEBUG #include "Utils.hpp" #include <fmt/format.h> #include <iostream> #include <string> using namespace std; static double const TEST_BASE = 0.9; double exponentiation(double base, int powerArg) noexcept { precondition(powerArg >= 0, "exponentiation() power must be non-negative, was " + to_string(powerArg)); int power = powerArg; double result = 1; while (power > 0) { result *= base; --power; } // This line will make the result incorrect. result = -result; // If power is odd and base is negative, then result should be negative. // Otherwise result should be positive. postcondition((power & 1) == 1 && (base < 0) ? result < 0 : result >= 0, "Postcondition Failed: Result is wrong sign"); return result; } int main(int argc, char **argv) { for (int p = 10; p >= -1; --p) { cout << fmt::format("{0:f} ^ {1:d} = {2:f}", TEST_BASE, p, exponentiation(TEST_BASE, p)) << endl; } return 0; }
Output
$ g++ -std=c++17 Assertions3.cpp -o Assertions3 -lfmt
$ ./Assertions3
Postcondition failed: Postcondition Failed: Result is wrong sign, File: Assertions3.cpp Line: 24.
Questions
- {{Who's on first?}}
- {{Who's on second?}}
- {{Who's on third?}}
Projects
More ★'s indicate higher difficulty level.
- Base Conversion
- Fast Exponentiation
- Fibonacci Numbers with Memoization
- Football Passer Rating (with Assertions)
- Julian Day Number
- Number of Primes (Estimate)
- Ordinal Date
- Ordinal Date (Revisited)
- Shuffle Deck
- Significant Digits
References
-
[[C++ Programming Language]], 4th Edition, Bjarne Stroustrup, Addison-Wesley, 2013, ISBN 978-0321563842.
- [[C++ Language Reference]]
- [[cplusplus.com]]
- [[Cprogramming.com]]