What function do we use in Julia in place of cin>> in C++? how to input number in Julia from keyboard? Can I create vector from keyboard in Julia?

function F(a=parse(Float64,readline()))
@show a
end

F()

You already found readline, which answers your first question.

It returns a string, which you have to process.

Look at ?parse and ?tryparse for parsing numbers.

To parse a vector, the best strategy is to split it to components (you could use Julia’s code parser, but that allows arbitrary code, so it is not recommended). Use split or regular expressions.

Why not? It’s not like it actually evaluates the code.

julia> function parsevector(T, str)
           expr = Meta.parse(str)
           if expr.head == :vect
             Vector{T}(expr.args)
           else
             error("could not parse")
           end
         end

julia> parsevector(Int, "[1, 2, 3]")
3-element Array{Int64,1}:
 1
 2
 3

The way you did it is OK I think (because nothing else should be able to get through); I was thinking of converting with eval.