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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: initial size of a std::vector of std::strings
Date: Wed, 07 Dec 2022 13:49:41 -0800
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Xref: csiph.com comp.lang.c++:87736

Lynn McGuire <lynnmcguire5@gmail.com> writes:
[...]
> I am trying to declare a vector with max_ncp strings in a struct.
> struct component_data {
> 	std::vector <std::string> component_names [max_ncp];
> 	doublereal heatoffusionatmeltingpoint [max_ncp];
> 	doublereal meltingpointtemperature [max_ncp];
> 	doublereal sublimationtemperature [max_ncp];
> 	doublereal triplepointtemperature [max_ncp];
> 	doublereal triplepointpressure [max_ncp];
> };
>
> Visual Studio 2015 does not like
>    	std::vector <std::string> component_names (max_ncp);
> or
> 	std::vector <std::string> component_names (max_ncp, "");

How does it express its dislike?  Both work for me:

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

int main() {
    int max_ncp = 42;
    {
        std::vector<std::string> component_names(max_ncp);
        std::cout << component_names.size() << ' ';
    }
    {
        std::vector<std::string> component_names(max_ncp, "");
        std::cout << component_names.size() << '\n';
    }
}

The output is "42 42".

> But it does like
> 	std::vector <std::string> component_names [max_ncp];
> But it does not work.

That defines an array (not a std::array, just a C-style array object) of
max_ncp vectors.  I think you want a single vector.

Do you want to set the initial size or the initial capacity?

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */