c-resources/CPlusPlus20ForProgrammers-m.../examples/ch08/fig08_09.cpp

56 lines
2.3 KiB
C++

// fig08_09.cpp
// C++17 string_view.
#include <fmt/format.h>
#include <iostream>
#include <string>
#include <string_view>
int main() {
std::string s1{"red"};
std::string s2{s1};
std::string_view v1{s1}; // v1 "sees" the contents of s1
std::cout << fmt::format("s1: {}\ns2: {}\nv1: {}\n\n", s1, s2, v1);
// string_views see changes to the characters they view
s1.at(0) = 'R'; // capitalize s1
std::cout << fmt::format("s1: {}\ns2: {}\nv1: {}\n\n", s1, s2, v1);
// string_views are comparable with strings or string_views
std::cout << fmt::format("s1 == v1: {}\ns2 == v1: {}\n\n",
s1 == v1, s2 == v1);
// string_view can remove a prefix or suffix
v1.remove_prefix(1); // remove one character from the front
v1.remove_suffix(1); // remove one character from the back
std::cout << fmt::format("s1: {}\nv1: {}\n\n", s1, v1);
// string_views are iterable
std::string_view v2{"C-string"};
std::cout << "The characters in v2 are: ";
for (char c : v2) {
std::cout << c << " ";
}
// string_views enable various string operations on C-Strings
std::cout << fmt::format("\n\nv2.size(): {}\n", v2.size());
std::cout << fmt::format("v2.find('-'): {}\n", v2.find('-'));
std::cout << fmt::format("v2.starts_with('C'): {}\n",
v2.starts_with('C'));
}
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