c++ - Cannot cast from vector<T> to T -


i have function takes arguments of type t such:

constexpr inline const bool isreflex(const t x1, const t y1, const t x2, const t y2, const t x, const t y)

calling function items form vector yiels error c2664: cannot convert argument 1 'vector<t, std::allocator<_ty>>' 'const t':

vector<t>* v = new vector<t>; // not creating vector myself, demonstration. // real vector passed const vector<t>* function executing following:  if (isreflex(v[i-2], v[i-1], v[i], v[i+1], v[i+2], v[i+3])) //           ^^^^^^ error

this makes little sense me, not passing vector rather contents. causing behaviour?

edit

ouch.

this because v not vector, pointer vector. therefore, need dereference operator:

if (isreflex((*v)[i-2], (*v)[i-1], (*v)[i], (*v)[i+1], (*v)[i+2], (*v)[i+3]))

the reason error message may not entirely clear [] operator applies pointers well, , behaves dereference operator offset. in other words, c++ compiler treats variable v built-in array of vectors, applies index [i-2] array, , reports error, because type of v[i-2] expression vector.

the real vector passed const vector<t>* function

you can make reference variable keep old syntax:

const vector<t> *pv // function parameter const vector<t>& v = *pv; // work if (isreflex(v[i-2], v[i-1], v[i], v[i+1], v[i+2], v[i+3])) {    ... }

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