How to best create bitstrings / binary data with known values with mixed types

Hi,

I have a general question about building bitstring/binary data. I have been following some articles that look at parsing binary data, so I feel like I have some handle on matching a binary, and bringing parts to variables, but I am having some difficulty creating binary data from known data with non-binary types.

# this makes sense to me
iex> <<first::binary-size(1), rest::binary>> = "hello world"
"hello world"
iex> first                                                  
"h"

# This also makes sense
iex> first                                               
"h"
iex> rest                                                
"ello world"
iex> <<first::binary, rest::binary>>                   
"hello world"

# But how now do I encode the integer 1 as a 4-or-8-byte block into the bitstring
iex> n = 1024                          
1024
iex> <<first::binary, _______, rest::binary>>

What I would hope to find out, is there a way for me to perform this in that form, or is the only way to do it is to go about it the long way:

iex(48)> first                                               
"h"
iex(49)> rest                                                
"ello world"
iex> n = 1024
1024
iex> n_as_bin = 
...>   n 
...>   |> :binary.encode_unsigned(:big) 
...>   |> :binary.bin_to_list() 
...>   |> (fn b -> List.duplicate(0, 4-length(b)) ++ b end).() 
...>   |> :binary.list_to_bin
<<0, 0, 4, 0>>
iex> <<first::binary, n_as_bin::binary, rest::binary>>                                                                                                    
<<104, 0, 0, 4, 0, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100>>

Thanks much in advance.