Print register better

[GiggleLiu]

Something like

julia> using BitBasis, Yao
julia> reg = rand_state(3)
ArrayReg{1, Complex{Float64}, Array...}
    active qubits: 3/3
julia> for (amp, b) in zip(state(reg), basis(BitStr64{nqubits(reg)}))
           println("$amp * $b")
       end
-0.3376505759988792 + 0.33325899072397025im * 000 ₍₂₎
0.32054579481565426 + 0.31927725422058706im * 001 ₍₂₎
0.09069334279111192 + 0.013173928388618843im * 010 ₍₂₎
-0.3263247507853093 - 0.07986342841304012im * 011 ₍₂₎
-0.27129613548559606 - 0.09708850865801441im * 100 ₍₂₎
-0.327171716777714 - 0.13959063658977386im * 101 ₍₂₎
0.23149778290317669 - 0.15132920651218748im * 110 ₍₂₎
-0.2859389557190614 + 0.28490459569435167im * 111 ₍₂₎

[Roger-luo]

I don't get it, why we need this at all? this won't work for large states and gives you no useful information about the state.

[GiggleLiu]

We can still print part of the state when the state is large, just as the julia vector printing. It can be implemented in another function, rather than the default show. Sometimes it is convenient.