# Adding a complex value to an element of a real array results in InexactError
**URL:** https://discourse.julialang.org/t/adding-a-complex-value-to-an-element-of-a-real-array-results-in-inexacterror/49271
**Category:** New to Julia
**Tags:** question
**Created:** [October 29, 2020, 10:37pm UTC](https://discourse.julialang.org/t/adding-a-complex-value-to-an-element-of-a-real-array-results-in-inexacterror/49271 "2020-10-29T22:37:40Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@useless-machine](https://discourse.julialang.org/u/useless-machine)
#### Post date: [October 29, 2020, 10:37pm UTC](https://discourse.julialang.org/t/adding-a-complex-value-to-an-element-of-a-real-array-results-in-inexacterror/49271/1 "2020-10-29T22:37:40Z")
Hi,
I’m just getting started with Julia and I’ve read that Julia does automatic conversion and promotion of variables, thus
```julia
U = 0
U = U + 1im
```
works properly. However, the following code
```julia
U = zeros(4)
U[2] = 1im
```
gives the error
```julia
ERROR: InexactError: Float64(0 + 1im)
Stacktrace:
[1] Real at .\complex.jl:37 [inlined]
[2] convert at .\number.jl:7 [inlined]
[3] setindex!(::Array{Float64,1}, ::Complex{Int64}, ::Int64) at .\array.jl:847
[4] top-level scope at REPL[9]:1
```
and I do not understand why.
---
### Author:  [@aramirezreyes](https://discourse.julialang.org/u/aramirezreyes)
#### Post date: [October 29, 2020, 11:17pm UTC](https://discourse.julialang.org/t/adding-a-complex-value-to-an-element-of-a-real-array-results-in-inexacterror/49271/2 "2020-10-29T23:17:28Z")
Your first line can be read as:
```julia
U = 0 #Save as U the integer zero
U = U + 1im #Add whatever is in U with the imaginary unit, and bind the result to the variable name U
```
When you add whatever is in U and the imaginary unit, Julia will promote them to the appropriate type (the integer zero can be promoted to a complex number `0 + 0i`. Then it performs the addition succesfully and stores the result with the name U.
In your second attempt you are doing something different:
```julia
U = zeros(4) #Create an array of length 4, where all the elements are of type `Float64` and fill it with zeros
U[2] = 1im # Store the imaginary unit as the second element of this array
```
In here your are first creating an array of Float64s. Then you are trying to store a complex number in that array. Julia tries to convert the Complex to a Float64 in order to store it in your array, but there is no correct way of doing this, since your would lose information. Therefore Julia throws an error indicating that a complex cannot be converted exactly into a float. This is the error you are seeing.
---
### Author:  [@useless-machine](https://discourse.julialang.org/u/useless-machine)
#### Post date: [October 29, 2020, 11:28pm UTC](https://discourse.julialang.org/t/adding-a-complex-value-to-an-element-of-a-real-array-results-in-inexacterror/49271/3 "2020-10-29T23:28:06Z")
Thanks for the extensive explanation.
So the best way is to overcome this problem is by directly assigning complex values to the array
```julia
U = zeros(4)im
```
---
### Author:  [@aramirezreyes](https://discourse.julialang.org/u/aramirezreyes)
#### Post date: [October 29, 2020, 11:33pm UTC](https://discourse.julialang.org/t/adding-a-complex-value-to-an-element-of-a-real-array-results-in-inexacterror/49271/4 "2020-10-29T23:33:56Z")
You can build the array of that type like:
```julia
U = zeros(Complex{Float64},4)
```