equal operator C++

Question

equal operator C++

Sid Kraft 46

have a C++ program, trying to assign a vector variable to a complex equation:

chm[i] = vec1[i] + (float cmid * vec2[i])/2.; i from 1 to 3

compiler generates an error that says "cannot find = operator to assign value define as vector from vectors and single value constant), variables as follows:

-cmid float single dimension variable

-vec1[i], vec2[i] vector <float> 3 dimension vector variables. any help available?

Darran Rowe 2,616 Reputation points

2026-05-25T21:38:43.8533333+00:00
Since you didn't give the type for chm, then no. That could be a class or structure that you define for all we know. It is always useful to give a small c++ sample, possibly commented, to illustrate your problem. Anything else will force anyone else to guess, and none of us knows anything about the libraries that you are using or even the intent of the code.

Also, even if you insist on giving things close to C++, make sure it is valid. C++ arrays are zero bound, so array indices of 1-3 on a 3 element array is going outside of the bounds of the array. You would always want to use 0-2. Yes, vector should be treated as an array here.

Anyway, as a basic example using vectors for chm too, so basically guessing, the above should compile.

#include <vector> extern"C" int main() { std::vector<float> vec1{ 1.f, 2.f, 3.f }; std::vector<float> vec2{ 4.f, 5.f, 6.f }; float cmid = 12.f; std::vector<float> chm(3); for (auto it = 0; it < 3; ++it) { chm[it] = vec1[it] + (cmid * vec2[it]) / 2; } return 0; }

You really should give a full and proper example of what you are trying to do.

2 answers

Your answer

Darran Rowe 2,616 Reputation points

2026-05-25T21:38:43.8533333+00:00

Since you didn't give the type for chm, then no. That could be a class or structure that you define for all we know. It is always useful to give a small c++ sample, possibly commented, to illustrate your problem. Anything else will force anyone else to guess, and none of us knows anything about the libraries that you are using or even the intent of the code.

Also, even if you insist on giving things close to C++, make sure it is valid. C++ arrays are zero bound, so array indices of 1-3 on a 3 element array is going outside of the bounds of the array. You would always want to use 0-2. Yes, vector should be treated as an array here.

Anyway, as a basic example using vectors for chm too, so basically guessing, the above should compile.

#include <vector> extern"C" int main() { std::vector<float> vec1{ 1.f, 2.f, 3.f }; std::vector<float> vec2{ 4.f, 5.f, 6.f }; float cmid = 12.f; std::vector<float> chm(3); for (auto it = 0; it < 3; ++it) { chm[it] = vec1[it] + (cmid * vec2[it]) / 2; } return 0; }

You really should give a full and proper example of what you are trying to do.

Answer 1

std::vector<float> does not have an overload of operator= that takes a single float. That is why the compiler reports it cannot find an = operator for assigning a vector from a scalar expression.

From the description, chm, vec1, and vec2 are std::vector<float> and cmid is float. Then:

chm[i] = vec1[i] + (float cmid * vec2[i]) / 2.;

operates on individual elements, so the type of the right-hand side is float, and chm[i] is also a float reference. This form is valid and should compile, because it uses the built‑in operator= for float.

The error typically appears when trying to assign the whole vector from a scalar expression, for example:

chm = vec1 + (cmid * vec2) / 2.0f;   // invalid for std::vector<float>

std::vector<float> does not define operator+, operator*, or operator/ between vectors and scalars, so the compiler cannot find a suitable overloaded operator (C2545 / C2446 style issues).

To fix this, either:

Work element‑wise (correct for std::vector<float>):

   for (size_t i = 0; i < 3; ++i) {
       chm[i] = vec1[i] + (cmid * vec2[i]) / 2.0f;
   }

Or, if chm, vec1, vec2 are custom vector types (for example a 3D vector class), ensure that:
- There is an operator= that assigns from the same vector type.
- There are overloaded operators such as operator+, operator* (scalar * vector), and operator/ (vector / scalar) with appropriate parameter types, as indicated by the error about not finding an overloaded operator.

If using a custom 3D vector type similar to CVEC3D, the class must provide the necessary arithmetic operators in addition to compound assignments like operator+= and operator-= that are already defined.

References:

Answer 2

Hello @Sid Kraft ,

It looks like you might be running into a couple of overlapping issues here. I would need to see the exact variable declarations to be entirely sure but based on the error message and the snippet you provided, below are a few thoughts from my side that might point you in the right direction.

1. Potential Syntax Issue First, the expression (float cmid * vec2[i]) might be confusing the compiler. If cmid is already declared as a floating-point variable earlier in your code, you shouldn't include the float type specifier in the middle of a mathematical equation. If you are trying to cast it, you should use (static_cast<float>(cmid) * vec2[i]), or simply (cmid * vec2[i]) if it's already a float.

2. The Vector Assignment Error The error message "cannot find = operator to assign value defined as vector..." typically suggests that the compiler thinks you are trying to perform mathematical operations on entire vector objects rather than scalar float values. In C++, the standard std::vector does not natively support mathematical operators like + or *. You cannot directly add two std::vector objects or multiply a vector by a scalar using these symbols out of the box.

Depending on how your variables are set up, it seems like one of two things is happening:

Possibility A (Element-wise): If vec1 and vec2 are declared simply as std::vector<float>, then vec1[i] represents a single float value, not a vector. In this case, simply fixing the cmid syntax mentioned above should resolve the problem:
```
    chm[i] = vec1[i] + (cmid * vec2[i]) / 2.0f;
```
(Also, as a quick side note: C++ uses 0-based indexing. If your vectors have 3 dimensions, your loop counter i should likely iterate from 0 to 2, rather than 1 to 3 to avoid out-of-bounds errors).
Possibility B (Nested Vectors): If vec1[i], vec2[i], and chm[i] represent entire mathematical vectors themselves (for example, if they are declared as std::vector<std::vector<float>>), the + and * operators won't work. You would either need to write a nested loop to calculate the values element by element, or consider using std::valarray instead of std::vector, as valarray is designed for numeric computations and natively supports these operators.

Could you share the specific lines of code where you declare chm, vec1, and vec2? That would help clarify what exact data types we are dealing with.

In the meantime, you might find these standard library references helpful regarding what operations are natively supported:

Let me know how those declarations look, and I'd be happy to help further. If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide for your confirmation.

Thank you.

Taki Ly (WICLOUD CORPORATION) 1,745 Reputation points Microsoft External Staff Moderator

2026-05-29T10:30:40.1266667+00:00

Hi @Sid Kraft ,

Have you seen my answer in this post? If you have any question, feel free to reach out. I'm happy to support you.
Taki Ly (WICLOUD CORPORATION) 1,745 Reputation points Microsoft External Staff Moderator

2026-06-02T09:37:27.75+00:00

Hi @Sid Kraft ,

As we haven’t heard back from you for a while, we’ll go ahead and close this thread for now. If you still need assistance later, feel free to create a new thread and share the link here so we can continue supporting you.

Thank you for your understanding.

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equal operator C++

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