Julia changing name in loop, using symbolic variables

问题

I'd like to change the name of a symbolic variable in each iteration of a loop, and then solve an equation using these symbolic variables e.g:

using SymPy
for i in 1:5
  p{i} = symbols("p"{i}, real=true,positive=true)
  solve(p{i}^2-i^2)
end

So I'm looking to create a series of scalar symbolic variables (since I don't think it is possible to create a vector valued symbolic variable) each with a different name - p1,p2,p3,p4 and p5 - and then use these in a equation solver. However the curly braces notation does not seem to work for naming in julia as per matlab. A quick google didn't suggest any obvious answers. Any ideas?

回答1:

In julia, and in most computer languages, if you find yourself needing a bunch of number variables x1, x2, x3, ... , you probably want an array. In julia this might look like this, (but note that I have no idea what I'm doing with SymPy)

using SymPy
pp=Sym[]
for i in 1:5
    p = symbols("x$i", real=true,positive=true)
    push!(pp,p)
    solve(pp[i]^2-i^2)
end

Here we start with pp empty, but of the right type; we push each symbol onto the end of pp; finally we can fish out the i'th item of the pp with pp[i], which is almost your code, but without the shift key.

来源：https://stackoverflow.com/questions/30999532/julia-changing-name-in-loop-using-symbolic-variables