Language: C++

#include<iostream>
#include<vector>
#include<math.h>
using namespace std;
#define EPS (1e-10)
#define equals(a,b) (fabs((a)-(b))<EPS)

#define FOR(k,m,n) for(int (k)=(m);(k)<(n);(k)++)
#define REP(i,n) FOR((i),0,(n))


//???

//???
class Point{
public:
	double x, y;
	//?????????????????????
	Point(double x_=0.0,double y_=0.0):x(x_),y(y_){}
	
	//??????????????????????????????
	Point operator + (Point &p) { return Point(x + p.x, y + p.y); }
	Point operator - (Point &p) { return Point(x - p.x, y - p.y); }
	Point operator * (double k) { return Point(x * k, y * k); }
	Point operator / (double k) { return Point(x / k, y / k); }

	bool operator  < (const Point &p)const {
		return x!=p.x ? x<p.x : y<p.y;
	}
	bool operator == (const Point &p)const {
		return fabs(x-p.x)<EPS && fabs(y-p.y)<EPS;
	}
};
typedef Point Vector;        //????????????
struct Segment{Point p1,p2;};//??????
typedef Segment Line;        //??´???

//???
class Circle {
public:
	Point center;
	double r;
	//?????????????????????
	Circle(Point c_=Point(),double r_=0.0):center(c_),r(r_){}
};
typedef vector<Point> Polygon;//????§???¢??????????????????



//??¢??°????????????
//????????¢??°??????
namespace PFunc {
	double norm(Point p) { return p.x*p.x + p.y*p.y; }
	double abs(Point p) { return sqrt(norm(p)); }
}

//?????????????????¢??°??????
namespace VFunc {
	//??????
	double dot(Vector a, Vector b) { return a.x*b.x + a.y*b.y; }
	//??????
	double cross(Vector a, Vector b) { return a.x*b.y - a.y*b.x; }
	//??´?????????????¨????
	bool isOrthogonal(Vector a, Vector b) { return equals(dot(a, b), 0.0); }
	bool isOrthogonal(Point a1,Point  a2, Point b1,Point b2) {return isOrthogonal(a1-a2,b1-b2);}
	bool isOrthogonal(Segment s1, Segment s2) { return equals(dot(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0); }
	//????????????????¨????
	bool isParallel(Vector a, Vector b) { return equals(cross(a, b), 0.0); }
	bool isParallel(Point a1, Point  a2, Point b1, Point b2) {return isParallel(a1 - a2, b1 - b2);}
	bool isParallel(Segment s1, Segment s2) {return equals(cross(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);}

	//?°???±
	Point project(Segment s, Point p) {
		Vector base = s.p2 - s.p1;
		double r = dot(p - s.p1, base) / PFunc::norm(base);
		return s.p1 + base*r;
	}
}

 
//?????°
Segment s;
int q;
Point temp,ans;

int main() {
	cin >> s.p1.x >> s.p1.y >> s.p2.x >> s.p2.y;
	cin>>q;
	REP(i, q) {
		cin>>temp.x>>temp.y;
		ans=VFunc::project(s,temp);
		cout<<ans.x<<" "<<ans.y<<endl;
	}
	cin>>q;
	return 0;
}

Compiler output:
a.cc: In function 'Point VFunc::project(Segment, Point)':
a.cc:76:29: error: no match for 'operator+' (operand types are 'Point' and 'Point')
   76 |                 return s.p1 + base*r;
      |                        ~~~~ ^ ~~~~~~
      |                          |        |
      |                          Point    Point
a.cc:22:15: note: candidate: 'Point Point::operator+(Point&)' (near match)
   22 |         Point operator + (Point &p) { return Point(x + p.x, y + p.y); }
      |               ^~~~~~~~
a.cc:22:15: note:   conversion of argument 1 would be ill-formed:
a.cc:76:35: error: cannot bind non-const lvalue reference of type 'Point&' to an rvalue of type 'Point'
   76 |                 return s.p1 + base*r;
      |                               ~~~~^~
In file included from /usr/include/c++/14/string:48,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::reverse_iterator<_Iterator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::move_iterator<_IteratorL>'
   76 |                 return s.p1 + base*r;
      |                                    ^
In file included from /usr/include/c++/14/string:54:
/usr/include/c++/14/bits/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   mismatched types 'const _CharT*' and 'Point'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   mismatched types 'const _CharT*' and 'Point'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   76 |                 return s.p1 + base*r;
      |                                    ^
/usr/include/c++/14/bits/basic_string.h:3740:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, _CharT)'
 3740 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3740:5: note:   template argument deduction/substitution failed:
a.cc:76:36: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocato