I am looking for a tutorial/package for a solver in Julia that is similar to fsolve in Matlab. My problem is mostly that I have a system of equations that I want to find a solution for. My system of equation however takes a vector of variables are given, which need to be included but are not to be solved for.

For anyone that is interested in a minimal example, although of course you donâ€™t need NLsolve to solve those equations

using NLsolve
f! = function (x,dx,a) # we want to find roots for f
dx[1] = x[1] - a[1]
dx[2] = x[2] - a[2]
end
a = [1;5]
g!(x,dx) = f!(x,dx,a) # g is our closure for a specific a
res = nlsolve(g!,[1.0;1.0])
res.zero # should give out [1;5] as the solution

Oh yeah thatâ€™s true, itâ€™s an anonymous function. Makes more sense, syntax wise. Got confused at first because the output said â€ś(::#1) (generic function with 1 method)â€ť

I should have been more careful: the machinery underlying generic and anonymous functions is the same. The main practical difference is that generic functions give a const binding, which allows you to add more methods, e.g. a regular binding gives:

julia> f = x -> x+1
(::#1) (generic function with 1 method)
julia> f(x,y) = 2
ERROR: cannot define function f; it already has a value

But if you make it const:

julia> const f = x -> x+1
(::#1) (generic function with 1 method)
julia> f(x,y) = 2
(::#1) (generic function with 2 methods)

The only remaining difference between this and the usual definition is the lack of a function name (which is really only for user convenience).