byte operation problem

[SherLzp]

Hi team, I have the problem for byte operations. For example: I have two byte array:

A []byte // size 20
B []byte // size 20

C := append(A, B) // size 40
CHash := mimc(C)

If I only put A,B into the circuit, how can I get the same result of CHash?

[SherLzp]

@gbotrel @ThomasPiellard

[SherLzp]

And another problem, if I have an array:

var A []Variable

Could I just use Select to decide to if I need to do an append operation.

My goal is to:

if flag{
    A = append(A, new value)
}