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Subscript requires array or pointer type

C++ add value into stack subscript requires array or pointer type and warning

I’m new to programming in C++. Also new to implementing stacks. My objective is creating RPN Calculator using template stack. Cant use the built in stack classes.

I have everything so far and now I am stuck, I can’t think of how to fix this problem. I am currently getting these errors:

This is my stack class:

This is my main class:

the problem seems to be coming from my push() method in the RPNCalculator template class.

1 answer

  • answered 2017-08-19 23:20 N00byEdge

Looks like you have a parameter for the function void push(T data); where the parameter has the same name as the class member ( data , your storage). Try changing the parameter name in the function implementation that doesn’t yield this conflict. You could also be specific which data you want to use if you really want to use that name.

Try this one instead

or, if you want to be explicit about which data you are assigning

This is usually avoided by naming the member variables in a way where there can’t be conflicts. One way is to prefix your members with m_ , where data would become m_data . Feel free to use any style of code that you want, but I’d suggest avoiding conflicts (and the second approach) when possible.

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Array declaration

Declares an object of array type.


[edit] Syntax

An array declaration is any simple declaration whose declarator has the form

A declaration of the form T a [ N ] ; , declares a as an array object that consists of N contiguously allocated objects of type T . The elements of an array are numbered 0, …, N — 1 , and may be accessed with the subscript operator [], as in a [ 0 ] , …, a [ N — 1 ] .

Arrays can be constructed from any fundamental type (except void ), pointers, pointers to members, classes, enumerations, or from other arrays of known bound (in which case the array is said to be multi-dimensional). In other words, only object types except for array types of unknown bound can be element types of array types. Array types of incomplete element type are also incomplete types.

There are no arrays of references or arrays of functions.

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Applying cv-qualifiers to an array type (through typedef or template type manipulation) applies the qualifiers to the element type, but any array type whose elements are of cv-qualified type is considered to have the same cv-qualification.

When used with new[]-expression, the size of an array may be zero; such an array has no elements:

[edit] Assignment

Objects of array type cannot be modified as a whole: even though they are lvalues (e.g. an address of array can be taken), they cannot appear on the left hand side of an assignment operator:

[edit] Array-to-pointer decay

There is an implicit conversion from lvalues and rvalues of array type to rvalues of pointer type: it constructs a pointer to the first element of an array. This conversion is used whenever arrays appear in context where arrays are not expected, but pointers are:

[edit] Multidimensional arrays

When the element type of an array is another array, it is said that the array is multidimensional:

Note that when array-to-pointer decay is applied, a multidimensional array is converted to a pointer to its first element (e.g., a pointer to its first row or to its first plane): array-to-pointer decay is applied only once.

[edit] Arrays of unknown bound

If expr is omitted in the declaration of an array, the type declared is «array of unknown bound of T», which is a kind of incomplete type, except when used in a declaration with an aggregate initializer:

Because array elements cannot be arrays of unknown bound, multidimensional arrays cannot have unknown bound in a dimension other than the first:

References and pointers to arrays of unknown bound can be formed, but cannot be initialized or assigned from arrays and pointers to arrays of known bound. Note that in the C programming language, pointers to arrays of unknown bound are compatible with pointers to arrays of known bound and are thus convertible and assignable in both directions.

Pointers to arrays of unknown bound cannot participate in pointer arithmetic and cannot be used on the left of the subscript operator, but can be dereferenced. Pointers and references to arrays of unknown bound cannot be used in function parameters (until C++14) .

[edit] Array rvalues

Although arrays cannot be returned from functions by value and cannot be targets of most cast expressions, array prvalues may be formed by using a type alias to construct an array temporary using brace-initialized functional cast.

Array xvalues may be formed directly by accessing an array member of a class rvalue or by using std::move or another cast or function call that returns an rvalue reference.

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