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  1.     //
  2.     //  main.cpp
  3.     //  TestConstness
  4.     //
  5.     //  Created by Marco Antognini on 27/10/13.
  6.     //  Copyright (c) 2013 Marco Antognini. All rights reserved.
  7.     //
  8.  
  9.     #include <iostream>
  10.     #include <memory>
  11.     #include <vector>
  12.  
  13.     class X {
  14.         int x;
  15.     public:
  16.         X(int y) : x(y) { }
  17.         void print() const { std::cout << "X::" << x << std::endl; }
  18.         void foo() { ++x; }
  19.     };
  20.  
  21.     using XPtr = std::shared_ptr<X>;
  22.     using ConstXPtr = std::shared_ptr<X const>;
  23.  
  24.     XPtr createX(int x) { return std::make_shared<X>(x); }
  25.  
  26.     void goo(XPtr p) {
  27.         p->print();
  28.         p->foo();
  29.         p->print();
  30.     }
  31.  
  32.     void hoo(ConstXPtr p) {
  33.         p->print();
  34.     //    p->foo(); // ERROR :-)
  35.     }
  36.  
  37.     using XsPtr = std::vector<XPtr>;
  38.     using ConstXsPtr = std::vector<ConstXPtr>;
  39.  
  40.     void ioo(ConstXsPtr xs) {
  41.         for (auto p : xs) {
  42.             p->print();
  43.     //        p->foo(); // ERROR :-)
  44.         }
  45.     }
  46.  
  47.     ConstXsPtr toConst(XsPtr xs) {
  48.         ConstXsPtr cxs(xs.size());
  49.         std::copy(std::begin(xs), std::end(xs), std::begin(cxs));
  50.         return cxs;
  51.     }
  52.  
  53.     void joo(XsPtr xs) {
  54.         for (auto p: xs) {
  55.             p->foo();
  56.         }
  57.     }
  58.  
  59.     // ERROR :-)
  60.     //XsPtr toNonConst(ConstXsPtr cxs) {
  61.     //    XsPtr xs(cxs.size());
  62.     //    std::copy(std::begin(cxs), std::end(cxs), std::begin(xs));
  63.     //    return xs;
  64.     //}
  65.  
  66.     class E {
  67.         XsPtr xs;
  68.     public:
  69.         E() {
  70.             for (auto i : { 2, 3, 5, 7, 11, 13 }) {
  71.                 xs.emplace_back(createX(std::move(i)));
  72.             }
  73.         }
  74.  
  75.         void loo() {
  76.             std::cout << "\n\nloo()" << std::endl;
  77.             ioo(toConst(xs));
  78.  
  79.             joo(xs);
  80.  
  81.             ioo(toConst(xs));
  82.         }
  83.  
  84.         void moo() const {
  85.             std::cout << "\n\nmoo()" << std::endl;
  86.             ioo(toConst(xs));
  87.  
  88.             joo(xs); // Should not be allowed
  89.  
  90.             ioo(toConst(xs));
  91.         }
  92.     };
  93.  
  94.     int main(int argc, const char * argv[])
  95.     {
  96.         std::cout << "Hello, World!\n";
  97.  
  98.         XPtr p = createX(42);
  99.  
  100.         goo(p);
  101.         hoo(p);
  102.  
  103.         E e;
  104.         e.loo();
  105.         e.moo();
  106.  
  107.         // WORKS!
  108.  
  109.         return 0;
  110.     }
  111.  
  112.  
Success #stdin #stdout 0s 3484KB
comments (?)
stdin
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Standard input is empty
stdout
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Hello, World!
X::42
X::43
X::43


loo()
X::2
X::3
X::5
X::7
X::11
X::13
X::3
X::4
X::6
X::8
X::12
X::14


moo()
X::3
X::4
X::6
X::8
X::12
X::14
X::4
X::5
X::7
X::9
X::13
X::15
https://ideone.com/DRv4RD
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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