begin() function on pointers/arrays

[SECMoG1T]

Hi am having problems understanding the difference between

a.

 #include <iostream>
  #include <algorithm>

  using namespace std;

  int main()
  {
   const char p[]="hello",p1[]="hello";

   cout<<((equal(begin(p),end(p),begin(p1)))?" equal" :" not equal");
   
   return 0;
  }
 

b.

  #include <iostream>
  #include <algorithm>

  using namespace std;

  int main()
  {
   const char *p="hello",*p1="hello";

   cout<<((equal(begin(p),end(p),begin(p1)))?" equal":" not equal");
   
   return 0;
  }

# problems are
1. i thought arrays can be explictly converted to pointers to their first
element and i am getting an error on the second example.

2. i understand that the generic equal function above uses the element type
operators to compare if elements are equal? but do c_style strings
const char p[]="hello",p1[]="hello"; really have == operator
or aren't this c_style strings?? this is because the first example is
working fine so i dont get where it gets == on const char* or does it use
strcmp()? or does it compare each element as a char using == ?

please help me understand this.

[MiiNiPaa]

i thought arrays can be explictly converted to pointers to their first
element and i am getting an error on the second example.

Yes, they can. Thing is, std::begin/end does not accept pointers as parameters.

but do c_style strings const char p[]="hello",p1[]="hello"; really have == operator or aren't this c_style strings??

No. Actually they do, but it compares addresses, not values.

this is because the first example is working fine so i dont get where it gets == on const char* or does it use strcmp()?

It uses neither. equal compares elements of sequence.

it works like:

while (begin1 != end!) {
    if (*begin1 != *begin2) break;
    ++begin1;
    ++begin2;
}
return begin1 == end1;

[SECMoG1T]

well @minnippa you said
Thing is, std::begin/end does not accept pointers as parameters but aren't
array parameters here

const char p[]="hello",p1[]="hello";

   cout<<((equal(begin(p),end(p),begin(p1)))?

same as pointers or what's going
on behind the hood? what exactly does begin() take?? coz an array parameter is simply
a pointer? not sure.

but now i know how begin() works if it is as show

  while (begin1 != end!) 
 {
    if (*begin1 != *begin2) break;
    ++begin1;
    ++begin2;
 }
 
return begin1 == end1;
   

but confused about its args. thank you for your time and hope you i'll help
me understand what are the actuall parameters passed to begin().

[MiiNiPaa]

aren't array parameters same as pointers

No. Your arrays have type const char[8] as opposed to const char*.

what exactly does begin() take

Overload related to arrays:

template <typename T, std::size_t N>
std::begin(T (&param)[N])

but now i know how begin() works if it is as show but confused about its args

That ws example of equal() finction, not begin(). begin1/2 is simply variable names here: bool equal(begin1, end1, begin2)

[SECMoG1T]

I was very confussed, i meant That ws example of equal() finction, not begin()
equal but thanks for correction.

now i get that begin() takes a reference to an array? yeah, excellent i hope i didn't read
that the wrong way.

thank you very much @minnippa now i understand.