foo.cc: In function 'int main()':
foo.cc:7:5: error: expected identifier before '(' token
  s=[(a+b)*h]/2
     ^
foo.cc: In lambda function:
foo.cc:7:13: error: expected '{' before '/' token
  s=[(a+b)*h]/2
             ^
foo.cc: In function 'int main()':
foo.cc:7:13: error: no match for 'operator/' (operand types are 'main()::<lambda()>' and 'int')
  s=[(a+b)*h]/2
In file included from /usr/include/c++/7/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/complex:416:5: note: candidate: template<class _Tp> std::complex<_Tp> std::operator/(const std::complex<_Tp>&, const std::complex<_Tp>&)
     operator/(const complex<_Tp>& __x, const complex<_Tp>& __y)
     ^~~~~~~~
/usr/include/c++/7/complex:416:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::complex<_Tp>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/complex:425:5: note: candidate: template<class _Tp> std::complex<_Tp> std::operator/(const std::complex<_Tp>&, const _Tp&)
     operator/(const complex<_Tp>& __x, const _Tp& __y)
     ^~~~~~~~
/usr/include/c++/7/complex:425:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::complex<_Tp>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52,
                 from foo.cc:1:
/usr/include/c++/7/complex:434:5: note: candidate: template<class _Tp> std::complex<_Tp> std::operator/(const _Tp&, const std::complex<_Tp>&)
     operator/(const _Tp& __x, const complex<_Tp>& __y)
     ^~~~~~~~
/usr/include/c++/7/complex:434:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   mismatched types 'const std::complex<_Tp>' and 'int'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from foo.cc:1:
/usr/include/c++/7/bits/valarray_after.h:405:5: note: candidate: template<class _Dom1, class _Dom2> std::_Expr<std::_BinClos<std::__divides, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__divides, typename _Dom1::value_type>::result_type> std::operator/(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::_Expr<_Dom2, typename _Dom2::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(/, __divides)
     ^
/usr/include/c++/7/bits/valarray_after.h:405:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from foo.cc:1:
/usr/include/c++/7/bits/valarray_after.h:405:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__divides, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__divides, typename _Dom1::value_type>::result_type> std::operator/(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)
     _DEFINE_EXPR_BINARY_OPERATOR(/, __divides)
     ^
/usr/include/c++/7/bits/valarray_after.h:405:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from foo.cc:1:
/usr/include/c++/7/bits/valarray_after.h:405:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__divides, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__divides, typename _Dom1::value_type>::result_type> std::operator/(const typename _Dom::value_type&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(/, __divides)
     ^
/usr/include/c++/7/bits/valarray_after.h:405:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from foo.cc:1:
/usr/include/c++/7/bits/valarray_after.h:405:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__divides, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__divides, typename _Dom1::value_type>::result_type> std::operator/(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::valarray<typename _Dom::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(/, __divides)
     ^
/usr/include/c++/7/bits/valarray_after.h:405:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/c++/7/valarray:592:0,
                 from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95,
                 from foo.cc:1:
/usr/include/c++/7/bits/valarray_after.h:405:5: note: candidate: template<class _Dom> std::_Expr<std::_BinClos<std::__divides, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__divides, typename _Dom1::value_type>::result_type> std::operator/(const std::valarray<typename _Dom::value_type>&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)
     _DEFINE_EXPR_BINARY_OPERATOR(/, __divides)
     ^
/usr/include/c++/7/bits/valarray_after.h:405:5: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0,
                 from foo.cc:1:
/usr/include/c++/7/valarray:1175:1: note: candidate: template<class _Tp> std::_Expr<std::_BinClos<std::__divides, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__divides, _Tp>::result_type> std::operator/(const std::valarray<_Tp>&, const std::valarray<_Tp>&)
 _DEFINE_BINARY_OPERATOR(/, __divides)
 ^
/usr/include/c++/7/valarray:1175:1: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::valarray<_Tp>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0,
                 from foo.cc:1:
/usr/include/c++/7/valarray:1175:1: note: candidate: template<class _Tp> std::_Expr<std::_BinClos<std::__divides, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__divides, _Tp>::result_type> std::operator/(const std::valarray<_Tp>&, const _Tp&)
 _DEFINE_BINARY_OPERATOR(/, __divides)
 ^
/usr/include/c++/7/valarray:1175:1: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   'main()::<lambda()>' is not derived from 'const std::valarray<_Tp>'
  s=[(a+b)*h]/2
              ^
In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0,
                 from foo.cc:1:
/usr/include/c++/7/valarray:1175:1: note: candidate: template<class _Tp> std::_Expr<std::_BinClos<std::__divides, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__divides, _Tp>::result_type> std::operator/(const _Tp&, const std::valarray<_Tp>&)
 _DEFINE_BINARY_OPERATOR(/, __divides)
 ^
/usr/include/c++/7/valarray:1175:1: note:   template argument deduction/substitution failed:
foo.cc:7:14: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
  s=[(a+b)*h]/2
              ^