CODEWITHSUNDEEP
c++stringvectorconstructorinitializer-list
oss
oss

Reputation: 115

Why is this declaration of a vector invalid?

The error I'm getting is "expected a ;".

    const int SIZE = 9;

    vector<string>possiblePalindromes(SIZE) = // error is shown here
        { "A man a plan a canal Panama",
          "The rain in Spain",
          "No lemon, no melon",
          "radar",
          "CS1D",
          "Was it a cat I saw?",
          "Racecar",
          "Saddleback",
          "dad" };

My question is, would this not be a valid declaration? The error goes away if I remove (SIZE), but my intention is to declare the vector with a specific size and a set of predefined values. That way when I decide to iterate through the vector, like 

for (int i = 0; i < SIZE; ++i)

I can refer to the SIZE of the vector directly, rather than some constant "9".

My inkling to this not working is that when I do

vector<string>possiblePalindromes(SIZE)

I am declaring the vector of size 9 with 9 string default values. Meaning that everything enclosed in the {} is not being read into the vector at all.

Upvotes: 2

Views: 738

Answers (3)

user12450543
user12450543

Reputation:

because one integral argument initialization of a vector object has been given, ie. its size, the initialization of the vector value is prevented.
Only either one may be declared at once.

may this help

  const int SIZE = 9;
  vector<string>possiblePalindromes =  //
        { "A man a plan a canal Panama",
          "The rain in Spain",
          "No lemon, no melon",
          "radar",
          "CS1D",
          "Was it a cat I saw?",
          "Racecar",
          "Saddleback",
          "dad" };


possiblePalindromes.resize(SIZE);     // decides the size now

for (int i = 0; i < SIZE; ++i)
   // ...

Upvotes: 0

Vlad from Moscow
Vlad from Moscow

Reputation: 310980

In fact you are trying to initialize an object of the type std::vector<std::string> using two constructors simultaneously.

The first constructor is the following

explicit vector(size_type n, const Allocator& = Allocator());

and the second constructor is

vector(initializer_list<T>, const Allocator& = Allocator());

This does not make sense.

You always can get the number of elements in a vector by using its member function size. And you always can resize a vector by using its method resize.

Moreover you can use the range-based for loop where knowing the number of elements is not required.

So just write

vector<string>possiblePalindromes = 
    { "A man a plan a canal Panama",
      "The rain in Spain",
      "No lemon, no melon",
      "radar",
      "CS1D",
      "Was it a cat I saw?",
      "Racecar",
      "Saddleback",
      "dad" };

Here is a demonstrative program

#include <iostream>
#include <string>
#include <vector>

int main() 
{
    std::vector<std::string> possiblePalindromes = 
    { 
        "A man a plan a canal Panama",
        "The rain in Spain",
        "No lemon, no melon",
        "radar",
        "CS1D",
        "Was it a cat I saw?",
        "Racecar",
        "Saddleback",
        "dad" 
    };

    std::cout << "The vecor contains " << possiblePalindromes.size() << " elements\n";

    std::cout << "They are:\n";

    for ( const auto &s : possiblePalindromes )
    {
        std::cout << '\t' << s << '\n';
    }

    return 0;
}

Its output is

The vecor contains 9 elements
They are:
    A man a plan a canal Panama
    The rain in Spain
    No lemon, no melon
    radar
    CS1D
    Was it a cat I saw?
    Racecar
    Saddleback
    dad

Upvotes: 3

Yksisarvinen
Yksisarvinen

Reputation: 22219

Or, if you want constant size, you can use std::array instead (note that size is a template argument like std::string, not passed in ()):

const int SIZE = 9; 

std::array<std::string, SIZE> possiblePalindromes = 
    { "A man a plan a canal Panama",
      "The rain in Spain",
      "No lemon, no melon",
      "radar",
      "CS1D",
      "Was it a cat I saw?",
      "Racecar",
      "Saddleback",
      "dad" };

Upvotes: 3

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