CODEWITHSUNDEEP
c++alias
林禹丞
林禹丞

Reputation: 11

Create an alias of variable?

I got a dilemma about creating an alias of variable and need your kind help.

Purpose

My function takes two vector, but I want to ensure that that vector variable "a" will refer to the longer one. At the same time, I don't want to copy the vector. So, I use the reference to create an alias, but I got a dilemma.

Situation 1

The variable can not be seen since the variable is in if clause, but I need the if clause to know which is longer.....

vector<float> conv(const vector<float> &operand1, const vector<float> &operand2){


if (operand1.size() < operand2.size()){
     const vector<float> &a = operand2;
     const vector<float> &b = operand1;
}
else{
    const vector<float> &a = operand1;
    const vector<float> &b = operand2;
}

Situation 2

Declare the reference outside the if clause. Unfortunately, the reference has to be initialized when declared. However, I need the if clause to know which operand to declare it as.

vector<float> conv(const vector<float> &operand1, const vector<float> &operand2){

const vector<float> &a;
const vector<float> &b;

if (operand1.size() < operand2.size()){
     &a = operand2;
     &b = operand1;
}
else{
     &a = operand1;
     &b = operand2;
}

Is there any way getting around this?? Thank you a lot.

Upvotes: 1

Views: 428

Answers (2)

Remy Lebeau
Remy Lebeau

Reputation: 595981

You can use pointers instead of references:

vector<float> conv(const vector<float> &operand1, const vector<float> &operand2)
{
    const vector<float> *a;
    const vector<float> *b;

    if (operand1.size() < operand2.size())
    {
        a = &operand2;
        b = &operand1;
    }
    else
    {
        a = &operand1;
        b = &operand2;
    }

    // use *a and *b as needed ...
}

Upvotes: 0

oxnz
oxnz

Reputation: 875

Is this you want:

vector<float> conv(const vector<float>& op1, const vector<float>& op2) {
    const vector<float> &a = op1.size() < op2.size() ? op2 : op1; // the longer one
    const vector<float> &b = op1.size() < op2.size() ? op1 : op2; // the other
    ...
}

Upvotes: 1

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