no match for 'operator !='

Question

A question from a C++ newbie. Forgive me if its a simple one.

I am trying to run a *.cpp code that reads a text file and outputs a formatted file. However when running the code, I am getting some compilation errors. I have attached herewith the code and errors.

The code:

#include<iostream>
#include<iomanip>
#include<fstream>
const int cell = 1;
using namespace std;
int main()
{
int id[cell],crop[cell],n;
double root_depth1[cell], root_depth2[cell], root_depth3[cell], root_fract1[cell], root_fract2[cell], root_fract3[cell], x;
double LAI_1[cell],LAI_2[cell],LAI_3[cell],LAI_4[cell],LAI_5[cell],LAI_6[cell];
double LAI_7[cell], LAI_8[cell], LAI_9[cell], LAI_10[cell], LAI_11[cell], LAI_12[cell];

ifstream read;

read.open("veg_par_in.txt");
if(read != 0)
{
    for (int i=0;i<cell;i++)
{
    read>>id[i]>>crop[i]>>root_depth1[i]>>root_fract1[cell]>>root_depth2[cell]>>root_fract2[cell]>>root_depth3[cell]>>root_fract3[cell];

    read>>LAI_1[i]>>LAI_2[i]>>LAI_3[i]>>LAI_4[i]>>LAI_5[i]>>LAI_6[i];
    read>>LAI_7[i]>>LAI_8[i]>>LAI_9[i]>>LAI_10[i]>>LAI_11[i]>>LAI_12[i];
}
read.close();
ofstream write;
write.open("veg_par.txt");
for(int j=0;j<cell;j++)
{
    write<<id[j]<<" "<<1<<endl;
    write<<right<<setw(5)<<crop[j]<<" "<<fixed<<setprecision(6)<<float(1)<<fixed<<setprecision(2)<<" "<<root_depth1[j]<<" "<<root_fract1[cell];
    write<<" "<<root_depth2[cell]<<" "<<root_fract2[cell]<<" "<<root_depth3[cell]<<" "<<root_fract3[cell]<<endl;
    write<<" "<<fixed<<setprecision(3)<<LAI_1[j]<<" "<<LAI_2[j]<< " "<<LAI_3[j]<<" "<<LAI_4[j]<<" "<<LAI_5[j]<," "<<LAI_6[j];
    write<<" "<<LAI_7[j]<<" "<<LAI_8[j]<<" "<<LAI_9[j]<<" "<<LAI_10[j]<<" "<<LAI_11[j]<<" "<<LAI_12[j]<<endl;
}
write.close();
}
else
    cout<<"veg_par_in.txt file is missing.";

}

The error message:

veg_par.cpp: In function ‘int main()’:

veg_par.cpp:17:10: error: no match for ‘operator!=’ (operand types are ‘std::ifstream {aka std::basic_ifstream<char>}’ and                               ‘int’)
if(read != 0)   
veg_par.cpp:17:10: note: candidate: operator!=(int, int) <built-in>
veg_par.cpp:17:10: note:   no known conversion for argument 1 from ‘std::ifstream {aka std::basic_ifstream<char>}’ to ‘in                               ’
   In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iosfwd:40:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/postypes.h:221:5: note: candidate: template<class _StateT> bool std::
operator!=(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
 operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/postypes.h:221:5: note:   template argument deduction/substitution fa                              iled:  
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::fpos<_StateT>’
 if(read != 0)
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_algobase.h:64:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/char_traits.h:39,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_pair.h:448:5: note: candidate: template<class _T1, class _T2> con                              stexpr bool std::operator!=(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_pair.h:448:5: note:   template argument deduction/substitution fa                              iled:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::pair<_T1, _T2>’    
if(read != 0)In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_algobase.h:67:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/char_traits.h:39,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:304:5: note: candidate: template<class _Iterator> bool                               std::operator!=(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
  operator!=(const reverse_iterator<_Iterator>& __x,
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:304:5: note:   template argument deduction/substitutio                              n failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::reverse_iterato                              r<_Iterator>’
 if(read != 0)
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_algobase.h:67:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/char_traits.h:39,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:

/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:361:5: note: candidate: template<class _IteratorL, cla                              ss _IteratorR> bool std::operator!=(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)
 operator!=(const reverse_iterator<_IteratorL>& __x,   
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:361:5: note:   template argument deduction/substitutio                              n failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::reverse_iterato                              r<_Iterator>’    
if(read != 0)
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_algobase.h:67:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/char_traits.h:39,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:

 /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:1125:5: note: candidate: template<class _IteratorL, cl                              ass _IteratorR> bool std::operator!=(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)
 operator!=(const move_iterator<_IteratorL>& __x,

/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:1125:5: note:   template argument deduction/substituti                              on failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::move_iterator<_                              IteratorL>’

if(read != 0)
           ^In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_algobase.h:67:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/char_traits.h:39,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:

/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:1131:5: note: candidate: template<class _Iterator> boo                              l std::operator!=(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)
 operator!=(const move_iterator<_Iterator>& __x,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/stl_iterator.h:1131:5: note:   template argument deduction/substituti                              on failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::move_iterator<_                              IteratorL>’

 if(read != 0)
         ^

In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/string:41:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_classes.h:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/ios_base.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:42,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/allocator.h:158:5: note: candidate: template<class _T1, class _T2> bo                              ol std::operator!=(const std::allocator<_CharT>&, const std::allocator<_T2>&)

 operator!=(const allocator<_T1>&, const allocator<_T2>&)
 ^~~~~~~~
  /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/allocator.h:158:5: note:   template argument deduction/substitution f                              ailed: 
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::allocator<_Char                              T>’
 if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/string:41:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_classes.h:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/ios_base.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:42,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:

/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/allocator.h:164:5: note: candidate: template<class _Tp> bool std::ope                              rator!=(const std::allocator<_CharT>&, const std::allocator<_CharT>&)
 operator!=(const allocator<_Tp>&, const allocator<_Tp>&)
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/allocator.h:164:5: note:   template argument deduction/substitution f                              ailed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::allocator<_Char                              T>’
 if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/string:52:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_classes.h:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/ios_base.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:42,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_string.h:5112:5: note: candidate: template<class _CharT, class                               _Traits, class _Alloc> bool std::operator!=(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_Ch                              arT, _Traits, _Alloc>&)
 operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_string.h:5112:5: note:   template argument deduction/substituti                              on failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::basic_string<_C                              harT, _Traits, _Alloc>’
 if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/string:52:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_classes.h:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/ios_base.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:42,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_string.h:5125:5: note: candidate: template<class _CharT, class                               _Traits, class _Alloc> bool std::operator!=(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
 operator!=(const _CharT* __lhs,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_string.h:5125:5: note:   template argument deduction/substituti                              on failed:
veg_par.cpp:17:13: note:   mismatched types ‘const _CharT*’ and ‘std::basic_ifstream<char>’
if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/string:52:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_classes.h:40,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/ios_base.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:42,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_string.h:5137:5: note: candidate: template<class _CharT, class                               _Traits, class _Alloc> bool std::operator!=(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
 operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_string.h:5137:5: note:   template argument deduction/substituti                              on failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::basic_string<_C                              harT, _Traits, _Alloc>’
if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/ios_base.h:46:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:42,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:

/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:311:3: note: candidate: bool std::operator!=(const std::error                              _code&, const std::error_code&)
operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:311:3: note:   no known conversion for argument 1 from ‘std::                              ifstream {aka std::basic_ifstream<char>}’ to ‘const std::error_code&’
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:315:3: note: candidate: bool std::operator!=(const std::error                              _code&, const std::error_condition&)
operator!=(const error_code& __lhs, const error_condition& __rhs) noexcept
^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:315:3: note:   no known conversion for argument 1 from ‘std::                              ifstream {aka std::basic_ifstream<char>}’ to ‘const std::error_code&’
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:319:3: note: candidate: bool std::operator!=(const std::error                              _condition&, const std::error_code&)
operator!=(const error_condition& __lhs, const error_code& __rhs) noexcept
^~~~~~~~
 /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:319:3: note:   no known conversion for argument 1 from ‘std::                              ifstream {aka std::basic_ifstream<char>}’ to ‘const std::error_condition&’
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:323:3: note: candidate: bool std::operator!=(const std::error                              _condition&, const std::error_condition&)
operator!=(const error_condition& __lhs,
^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/system_error:323:3: note:   no known conversion for argument 1 from ‘std::                   ifstream {aka std::basic_ifstream<char>}’ to ‘const std::error_condition&’
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_facets.h:48:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/basic_ios.h:37,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ios:44,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/ostream:38,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iostream:39,
             from veg_par.cpp:2:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/streambuf_iterator.h:210:5: note: candidate: template<class _CharT, c                   lass _Traits> bool std::operator!=(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT                   , _Traits>&)
 operator!=(const istreambuf_iterator<_CharT, _Traits>& __a,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/streambuf_iterator.h:210:5: note:   template argument deduction/subst                   itution failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::istreambuf_iter                   ator<_CharT, _Traits>’
if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/tuple:39:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:37,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_conv.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/locale:43,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iomanip:43,
             from veg_par.cpp:3:


/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/array:246:5: note: candidate: template<class _Tp, long unsigned int _Nm> b                   ool std::operator!=(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)
 operator!=(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/array:246:5: note:   template argument deduction/substitution failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::array<_Tp, _Nm                    ’
if(read != 0)
         ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:37:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_conv.h:41,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/locale:43,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iomanip:43,
             from veg_par.cpp:3:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/tuple:1367:5: note: candidate: template<class ... _TElements, class ... _U                   Elements> constexpr bool std::operator!=(const std::tuple<_Elements ...>&, const std::tuple<_Elements ...>&)
 operator!=(const tuple<_TElements...>& __t,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/tuple:1367:5: note:   template argument deduction/substitution failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::tuple<_Elements                    ...>’
if(read != 0)
           ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_conv.h:41:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/locale:43,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iomanip:43,
             from veg_par.cpp:3:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:667:5: note: candidate: template<class _Tp, class _Dp, c                   lass _Up, class _Ep> bool std::operator!=(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)
 operator!=(const unique_ptr<_Tp, _Dp>& __x,
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:667:5: note:   template argument deduction/substitution                    failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::unique_ptr<_Tp,                    _Dp>’
if(read != 0)
           ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_conv.h:41:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/locale:43,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iomanip:43,
             from veg_par.cpp:3:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:673:5: note: candidate: template<class _Tp, class _Dp> b                   ool std::operator!=(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)
 operator!=(const unique_ptr<_Tp, _Dp>& __x, nullptr_t) noexcept
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:673:5: note:   template argument deduction/substitution                    failed:
veg_par.cpp:17:13: note:   ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘const std::unique_ptr<_Tp,                    _Dp>’
if(read != 0)
           ^
In file included from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/locale_conv.h:41:0,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/locale:43,
             from /usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/iomanip:43,
             from veg_par.cpp:3:
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:678:5: note: candidate: template<class _Tp, class _Dp> b                   ool std::operator!=(std::nullptr_t, const std::unique_ptr<_Tp, _Dp>&)
 operator!=(nullptr_t, const unique_ptr<_Tp, _Dp>& __x) noexcept
 ^~~~~~~~
/usr/lib/gcc/x86_64-pc-cygwin/6.4.0/include/c++/bits/unique_ptr.h:678:5: note:   template argument deduction/substitution                    failed:
veg_par.cpp:17:13: note:   mismatched types ‘const std::unique_ptr<_Tp, _Dp>’ and ‘int’
if(read != 0)
         ^
veg_par.cpp:34:109: error: expected primary-expression before ‘,’ token
write<<" "<<fixed<<setprecision(3)<<LAI_1[j]<<" "<<LAI_2[j]<< " "<<LAI_3[j]<<" "<<LAI_4[j]<<" "<<LAI_5[j]<," "<<LAI_6[j                   ];
                                                                                                         ^
veg_par.cpp:34:113: error: invalid operands of types ‘const char [2]’ and ‘double’ to binary ‘operator<<’
write<<" "<<fixed<<setprecision(3)<<LAI_1[j]<<" "<<LAI_2[j]<< " "<<LAI_3[j]<<" "<<LAI_4[j]<<" "<<LAI_5[j]<," "<<LAI_6[j                   ];
                                                                                                          ~~~^~~~~~~~~                   ~

The first error says there is no match for 'operator!=' with operand types char and int. I have been looking into this error and found out this may be related with the operator comparing two types of operand types. Here, 'read' is a stream variable and it has a data type of char and the operator is comparing two data types. I am pretty sure that all the errors while running this code arises from the operator comparing the two data types.

I used "g++ -g veg_par.cpp -o a.exe" for compilation.

How do I solve this error? Any help would be highly appreciated.

Answer 1

The first error says there is no match for 'operator!=' with operand types char and int

Not quite. Your problem is in this expression read != 0. It's attempting to compare an std::ifstream to an int. Since the former is a class type, overloaded operators must by considered, as well as any user defined conversions to int. There are no such conversions, and no operator!= defined. So you can't write such a comparison.

Now, that does't mean you use read in the condition of an if-statement. It just means you must use it in one of the supported ways. Those being if(read) and if(!read). std::ifstream has an operator! as well is allowing contextual conversions to bool.