C++

Everything that applies to C also applies to C++. This article contains only things that don't apply to C.

Overall philosophy

I believe that a programming language should be designed to make simple things simple and complex things as simple as possible. C++ is designed to make simple things complex and complex things even more complex. For example, a program to read space-separated numbers from STDIN, sort them and again output them space-separated:

Python 3

nums = [int(inp) for inp in input().split()]
print(*sorted(nums))

Try it online!

Nim

import std/[strutils, sequtils, algorithm]

let nums = stdin.readLine.splitWhitespace.mapIt(it.parseInt)
echo nums.sorted.mapIt($it).join(" ")

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Haskell

import Data.List

main = interact $ (++ "\n") . unwords . map show
                . sort
                . map (read :: String -> Int) . words

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#include <iostream>
#include <vector>
#include <algorithm>

int main() {
  std::vector<int> nums;
  std::string inp;
  while (std::getline(std::cin, inp, ' ')) {
    nums.emplace_back(std::stoi(inp));
  }
  std::sort(nums.begin(), nums.end());
  std::string sep = "";
  for (int num : nums) {
    std::cout << sep << num;
    sep = " ";
  }
  std::cout << std::endl;
}

Try it online!

Features

Despite being a very large language, C++ doesn't have basic features like sum types or pattern matching.
Many features duplicate other features, adding their own advantages and drawbacks (and more unnecessary syntactic rules to learn). Examples: initializer lists, typedef / using, #define / constexpr, char[] / std::string, int[] / std::array<int>, printf / cout, struct / class

Syntax

C++ took the horrible syntax of C and somehow managed to make it even worse.

The most vexing parse (and similar rules). I can't fathom what could possibly cause someone to think this is a good idea.
Parsing C++ is literally undecidable.
Using less-than and greater-than signs as brackets, which hinders auto-pairing and complicates parsing while also looking ugly. Here's a longer explanation from another person.
The semicolon after a struct / class definition. Just why?
Keywords that have multiple meanings depending on where you use them: static, using, typename.
The keyword const is used to declare immutable variables (not constants, for which there is constexpr) and it can be placed in various positions inside a type, which completely changes its meaning.
Who decided that :: is a good path separator?

Standard library

Despite being quite extensive, the standard library doesn't have basic things like
- basic functions for working with strings (split, join)
- functional abstractions (map, filter, fold, …) [C++20 partially solves this with “range adaptors” (what a weird name), but the usage is unbearably cumbersome]
- optional/result types
Using the term “vector” for a resizable array, even though the word has a completely different meaning in mathematics.
There is no convenient way to pass a whole array/vector/list to a function, you have to do something like std::sort(arr.begin(), arr.end()).
Weird function names: from C crypticisms (stoi, fscanf) to unusual words (emplace_back).
Idiomatically, it's required to write std:: between everything from the standard library, which makes the code repetitive and unreadable. Who would have guessed that sort is a standard library function if it wasn't for the prefix?

Tooling

Error messages.

If you try to search a “vector” (array) of a wrong type… Credit goes to this StackExchange answer.

#include <vector>
#include <algorithm>

int main() {
    int a;
    std::vector<std::vector<int>> v;
    std::vector<std::vector<int>>::const_iterator it = std::find(v.begin(), v.end(), a);
}

Try it online! The error message (compiled with GCC 10.2.0) has 148 lines with about 12 kB of content, starting with:

In file included from /usr/include/c++/10.2.0/bits/stl_algobase.h:71,
                 from /usr/include/c++/10.2.0/vector:60,
                 from error.cpp:1:
/usr/include/c++/10.2.0/bits/predefined_ops.h: In instantiation of ‘bool __gnu_cxx::__ops::_Iter_equals_val<lt;_Value>::operator()(_Iterator) [with _Iterator = __gnu_cxx::__normal_iterator<lt;std::vector<lt;int>*, std::vector<lt;std::vector<lt;int> > >; _Value = const int]’:
/usr/include/c++/10.2.0/bits/stl_algobase.h:1932:14:   required from ‘_RandomAccessIterator std::__find_if(_RandomAccessIterator, _RandomAccessIterator, _Predicate, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<lt;std::vector<lt;int>*, std::vector<lt;std::vector<lt;int> > >; _Predicate = __gnu_cxx::__ops::_Iter_equals_val<lt;const int>]’
/usr/include/c++/10.2.0/bits/stl_algobase.h:1977:23:   required from ‘_Iterator std::__find_if(_Iterator, _Iterator, _Predicate) [with _Iterator = __gnu_cxx::__normal_iterator<lt;std::vector<lt;int>*, std::vector<lt;std::vector<lt;int> > >; _Predicate = __gnu_cxx::__ops::_Iter_equals_val<lt;const int>]’
/usr/include/c++/10.2.0/bits/stl_algo.h:3902:28:   required from ‘_IIter std::find(_IIter, _IIter, const _Tp&) [with _IIter = __gnu_cxx::__normal_iterator<lt;std::vector<lt;int>*, std::vector<lt;std::vector<lt;int> > >; _Tp = int]’
error.cpp:7:87:   required from here
/usr/include/c++/10.2.0/bits/predefined_ops.h:268:17: error: no match for ‘operator==’ (operand types are ‘std::vector<lt;int>’ and ‘const int’)
  268 |  { return *__it == _M_value; }
      |           ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/10.2.0/bits/stl_algobase.h:67,
                 from /usr/include/c++/10.2.0/vector:60,
                 from error.cpp:1:
/usr/include/c++/10.2.0/bits/stl_iterator.h:1064:5: note: candidate: ‘template<lt;class _IteratorL, class _IteratorR, class _Container> bool __gnu_cxx::operator==(const __gnu_cxx::__normal_iterator<lt;_IteratorL, _Container>&, const __gnu_cxx::__normal_iterator<lt;_IteratorR, _Container>&)’
 1064 |     operator==(const __normal_iterator<lt;_IteratorL, _Container>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10.2.0/bits/stl_iterator.h:1064:5: note:   template argument deduction/substitution failed:

If you forget a semicolon… Credit goes to this StackExchange answer.

constexpr double pi = 3.0 // An engineer approximation

#include <iostream>

int main() {
  std::cout << "Enter the radius: " << std::flush;
  double radius;
  std::cin >> radius;
  std::cout << "Area: " << pi * radius * radius << std::endl;
}

Try it online! The error message (compiled with GCC 10.2.0) has 3244 lines with about 250 kB of content, starting with:

In file included from /usr/include/c++/10.2.0/iostream:38,
  from error.cpp:3:
/usr/include/c++/10.2.0/x86_64-pc-linux-gnu/bits/c++config.h:258:1: error: expected ‘,’ or ‘;’ before ‘namespace’
  258 | namespace std
      | ^~~~~~~~~
In file included from /usr/include/c++/10.2.0/iosfwd:40,
  from /usr/include/c++/10.2.0/ios:38,
    from /usr/include/c++/10.2.0/ostream:38,
      from /usr/include/c++/10.2.0/iostream:39,
        from error.cpp:3:
/usr/include/c++/10.2.0/bits/postypes.h:98:11: error: ‘ptrdiff_t’ does not name a type
  98 |   typedef ptrdiff_t streamsize; // Signed integral type
     |           ^~~~~~~~~
/usr/include/c++/10.2.0/bits/postypes.h:41:1: note: ‘ptrdiff_t’ is defined in header ‘<cstddef>’; did you forget to ‘#include <cstddef>’?
  40 | #include <cwchar> // For mbstate_t
 +++ |+#include <cstddef>
  41 | 
In file included from /usr/include/c++/10.2.0/bits/exception_ptr.h:40,
  from /usr/include/c++/10.2.0/exception:147,
    from /usr/include/c++/10.2.0/ios:39,
      from /usr/include/c++/10.2.0/ostream:38,
        from /usr/include/c++/10.2.0/iostream:39,
          from error.cpp:3:
/usr/include/c++/10.2.0/new:126:26: error: declaration of ‘operator new’ as non-function
  126 | _GLIBCXX_NODISCARD void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
      |                          ^~~~~~~~
/usr/include/c++/10.2.0/new:126:44: error: ‘size_t’ is not a member of ‘std’; did you mean ‘size_t’?
  126 | _GLIBCXX_NODISCARD void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
      |                                            ^~~~~~

I guess the fourth line does tell you that you missed a semicolon (if you have the patience to scroll to it), but it's not exactly clear where.

Would you prefer an error that I actually encountered? Here is a simplified version of some code I wrote in a programming contest:

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <vector>

std::string decrypt(std::string& k, std::string& m) {
  std::vector<std::string> c(k.length());
  int n = m.length() % k.length() == 0 ? m.length() / k.length() : m.length() / k.length() + 1;
  int a = 0;
  for (std::string& s : c) {
    for (int i = 0; i < n; i++) {
      s += a >= m.length() ? ' ' : m[a];
      a++;
    }
  }
  std::vector<int> j(k.length());
  std::iota(j.begin(), j.end(), 0);
  std::sort(j.begin(), j.end(), [&k](int x, int y) { return k[x] < k[y]; });
  std::vector<int> q(k.length());
  for (int i = 0; i < k.length(); i++) {
    q[j[i]] = i;
  }
  std::string r = "";
  for (int i = 0; i < n; i++) {
    for (int ii = 0; ii < k.length(); ii++) {
      char h = c[q[ii]][i];
      if (c != ' ') {
        r += c;
      }
    }
  }
  return r;
}

int main() {
  std::string k;
  std::getline(std::cin, k);
  std::string m;
  std::getline(std::cin, m);
  std::cout << decrypt(k, m) << std::endl;
}

Try it online! The error message does tell you where the error is, but you have to scroll through 228 lines with over 22 kB of content.

C++ Language Criticism

Overall philosophy

Python 3

Nim

Haskell

C++

Features

Syntax

Standard library

Tooling