Chapter 1 examples

chapter_01/examples/CMakeLists.txt

+cmake_minimum_required(VERSION 3.28)
+set(CMAKE_CXX_EXTENSIONS OFF)
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+project(cxx_course_examples CXX)
+
+
+FILE (GLOB sources ./ *.cc)
+foreach(source ${sources})
+    get_filename_component(withoutext "${source}" NAME_WE)
+    add_executable("${withoutext}" "${source}")
+endforeach()
+
+

chapter_01/examples/binforms.cc

+#include "binform.hh"
+#include <iostream>
+
+template <class T>
+void handle()
+{
+    std::cout << "Enter value: ";
+    T v;
+    std::cin >> v;
+    cxx_course::showbits(v);
+}
+
+auto main() -> int
+{
+    bool keeplooping{true};
+    while (keeplooping) {
+        int ch{};
+        std::cout << "Select type (1: int, 2: unsigned int, 3: long, 4: unsigned long, 5: float, 6: double): ";
+        std::cin >> ch;
+        switch (ch) {
+        case 1: 
+            handle<int>(); break;
+        case 2: 
+            handle<unsigned int>(); break;
+        case 3: 
+            handle<long>(); break;
+        case 4: 
+            handle<unsigned long>(); break;
+        case 5: 
+            handle<float>(); break;
+        case 6: 
+            handle<double>(); break;
+        case 0: keeplooping = false; break;
+        default:;
+        };
+    }
+}
+

chapter_01/examples/check_prime.cc

+#include <iostream>
+
+auto is_prime(unsigned int n) -> bool
+{
+    // recipe to tell if n is a prime or not
+    return false;
+}
+
+auto main() -> int
+{
+    std::cout << "Number to check: ";
+    unsigned int inp{};
+    std::cin >> inp;
+    if (is_prime(n))
+        std::cout << "Yes, that's a prime.\n";
+    else
+        std::cout << "Not a prime.\n";
+}
+
+

chapter_01/examples/dangling_pr/outer_ptr.cc

+#include <iostream>
+#include <string>
+
+auto main(int argc, char* argv[]) -> int
+{
+    unsigned long* p = nullptr;
+    if (argc > 1) {
+        auto i = std::stoul(argv[1]);
+
+        p = &i; 
+        // Since p outlives i, storing address 
+        // of i in p is a bad idea
+
+        std::cout << "p is pointing at " << p << " storing a value " << *p << "\n";
+    } else {
+        std::cout << "Needs one integer command line argument!\n";
+    }
+
+    // At this point, if argc > 1, p is pointing to
+    // a location where there was a variable called i
+    // which has run out of scope. Accessing p here is
+    // undefined behaviour.
+    if (p)
+        std::cout << "p is pointing at " << p << " storing a value " << *p << "\n";
+}
+

chapter_01/examples/dangling_pr/ref_heap.cc

+#include <vector>
+#include <iostream>
+
+auto main() -> int
+{
+    std::vector v{1, 2, 3};
+    const auto& vstart = v.front();
+    v.push_back(4);
+    v.push_back(5);
+    v.push_back(6);
+    v.push_back(7);
+    v.push_back(8);
+    std::cout << "Start element of v = " << vstart << "\n";
+}
+

chapter_01/examples/dangling_pr/ref_local.cc

+#include <iostream>
+#include <string>
+
+auto f(double x) -> double&
+{
+    auto y = x * x;
+    return y;
+}
+
+auto main() -> int
+{
+    auto a = 4.0;
+    auto&& z = f(a);
+    std::cout << z << "\n";
+}
+

chapter_01/examples/exception.cc

+#include <iostream>
+#include <stdexcept>
+
+double f(double x) 
+{
+    double answer=1;
+    if (x>=0 and x<10) {
+        while (x>0) {
+            answer*=x;
+            x-=1;
+        }
+    } else {
+        throw(std::invalid_argument("Bad parameter value " + std::to_string(x)));
+    }
+    return answer;
+}
+
+
+int main()
+{
+    double x=9.0;
+    try {
+        std::cout<<"Enter start point : ";
+        std::cin >> x;
+        auto res=f(x);
+        std::cout <<"The result is "<<res<<'\n';
+    } catch (std::exception &ex) {
+        std::cerr<<"Cought exception "<<ex.what()<<'\n';
+    }
+}
+
+

chapter_01/examples/fibonacci.cc

+#include <iostream>
+#include <limits>
+#include <format>
+
+auto main() -> int
+{
+    using namespace std;
+    size_t umax{ numeric_limits<size_t>::max() };
+    unsigned nfib = 0;
+    size_t f0{ 0 }, f1{ 1 };
+    // Insert your code here
+
+    cout << format(R"(The largest number in the Fibonacci sequence under {0:} is {1:},
+and there are {2:} entries under {0:} in that sequence.
+)"                 , umax, f1, nfib);
+}

chapter_01/examples/gcd.cc

+#include <iostream>
+
+auto euclid_gcd(unsigned long smaller, unsigned long larger) -> unsigned long 
+{
+    if (smaller > larger)
+        std::swap(smaller, larger);
+    // Fill in your code to implement Euclid's algorithm here.
+
+    return ? ? ? ;
+}
+
+auto main(int argc, char* argv[]) -> int
+{
+    if (argc != 3) {
+        std::cout << "Usage:\n"
+                  << argv[0] << " number1 number2\n";
+        return 1;
+    }
+    unsigned long n1 = std::stoul(argv[1]), n2 = std::stoul(argv[2]);
+    std::cout << euclid_gcd(n1, n2) << "\n";
+}

chapter_01/examples/hanoi.cc

+#include <iostream>
+#include <string>
+
+auto the_other(int i, int j) -> int { return 3 - i - j; }
+
+void transfer(unsigned long n, int from, int to)
+{
+    int oth = the_other(from, to);
+    if (n > 1)
+        transfer(n - 1, from, oth);
+    std::cout << n << ": " << from << "->" << to << "\n";
+    if (n > 1)
+        transfer(n - 1, oth, to);
+}
+
+auto main() -> int
+{
+    size_t N = 6;
+    transfer(N, 0, 1);
+}

chapter_01/examples/hello_qa.cc

+// examples/hello_qa.cc
+#include <string>
+#include <iostream>
+
+auto main() -> int
+{
+    std::string name;
+    std::cout << "What's your name ? ";
+    std::cin >> name;
+    std::cout << "Hello, " << name << "\n";
+}
+

chapter_01/examples/hello_xyz.cc

+// examples/hello_xyz.cc
+#include <iostream>
+auto main(int argc, char* argv[]) -> int
+{
+    std::cout << "Hello, ";
+    if (argc > 1)
+        std::cout << argv[1] << "!\n";
+    else
+        std::cout << "world!\n";
+}

chapter_01/examples/midpt.cc

+// examples/midpt.cc
+#include <iostream>
+
+auto mid(int a, int b) -> int
+{
+    // recipe needed!
+    return a;
+}
+auto main() -> int
+{
+    int i = 0, j = 0;
+    std::cout << "Enter i, j: ";
+    std::cin >> i >> j;
+    std::cout << "A number half way between " << i << " and " << j
+              << " is " << mid(i, j) << "\n";
+}
+

chapter_01/examples/min_of_three.cc

+// examples/min_of_three.cc
+#include <iostream>
+
+auto min_of_three(int a, int b, int c) -> int
+{
+    // recipe needed!
+    return a;
+}
+auto main() -> int
+{
+    int i = 0, j = 0, k = 0;
+    std::cout << "Enter i, j and k: ";
+    std::cin >> i >> j >> k;
+    std::cout << "The smallest of the three is " << min_of_three(i, j, k) << "\n";
+}
+

chapter_01/examples/namespaces.cc

+#include <iostream>
+
+using namespace std;
+
+namespace UnitedKingdom {
+string London = "Big city";
+}
+namespace UnitedStates {
+string London = "Small town in Kentucky";
+}
+auto main() -> int
+{
+    using namespace UnitedKingdom;
+    cout << London << "\n";
+    cout << UnitedStates::London << "\n";
+}

chapter_01/examples/namespaces2.cc

+#include <iostream>
+namespace UnitedKingdom {
+std::string London = "Big city";
+}
+namespace UnitedStates {
+namespace KY {
+    std::string London = "Small town in Kentucky";
+}
+namespace OH {
+    std::string London = "Small town in Ohio";
+}
+}
+// The following definition is ok since C++17
+//namespace mylibrary::onefeature {
+//    double solve(int i);
+//}
+auto main() -> int
+{
+    namespace USOH = UnitedStates::OH;
+    std::cout << USOH::London << "\n";
+}
+

chapter_01/examples/numsort.cc

+#include <iostream>
+#include <string>
+#include <fstream>
+#include <filesystem>
+#include <vector>
+#include <ranges>
+#include <algorithm>
+
+namespace fs = std::filesystem;
+auto as_lines(fs::path file) -> std::vector<std::string>
+{
+    std::ifstream fin{ file };
+    std::string line;
+    std::vector<std::string> lines;
+    while (getline(fin, line)) lines.push_back(line);
+    return lines;
+}
+
+auto main(int argc, char* argv[]) -> int
+{
+    if (argc != 2) {
+        std::cerr << "Usage:\n"
+                  << argv[0] << " filename\n";
+        return 1;
+    }
+    auto content = as_lines(argv[1]);
+    std::ranges::sort(content,
+                 [](auto l1, auto l2) {
+                     return std::stod(l1) < std::stod(l2);
+                 }
+             );
+    for (std::string_view line : content) {
+        std::cout << line << "\n";
+    }
+}
+

chapter_01/examples/onespace.cc

+// examples/onespace.cc
+#include <iostream>
+
+auto main(int argc, char* argv[]) -> int
+{
+    std::string line;
+    while (getline(std::cin, line)) {
+        if (line.empty()) {
+            continue;
+        }
+        bool sp{true};
+        for (auto c : line) {
+            if (isspace(c)) {
+                if (not sp) std::cout << '\t';
+                sp = true;
+            } else {
+                sp = false;
+                std::cout << c;
+            }
+        }
+        std::cout << "\n";
+    }
+}
+

chapter_01/examples/pyscope2.py

+import sys
+if __name__ == "__main__":
+    if len(sys.argv) > 1:
+        N = int(sys.argv[1])
+    else:
+        N = 5
+
+def fact(n):
+    if n > 1:
+        return n * fact(n-1)
+    return 1
+while N > 0:
+    print(fact(N))
+    if N % 4 == 0:
+        fact = N * (N - 1) / 2
+    N = N -1
+

chapter_01/examples/raw1.cc

+#include <iostream>
+#include <string>
+
+int main()
+{
+    std::cout << "Use a single backslash character at the end of the line to continue input to the next line, as shown ...\n"
+              << "OBJ=a.o \\\n\tb.o\\\n\tc.o\n";
+}