Explicitly typed symbols do not have base functions associated with them

[leios]

The type Array is expected to have some functions available like length(...) or reshape!(...), but when trying to build a symbolic tree, these functions are not available.

Here, I tried to create 2 arrays (x, and y) and add length(y) to x.

julia> using SymbolicUtils

julia> @syms x::Array y::Array
(x, y)

julia> z = x^2 .+ length(y)
ERROR: MethodError: no method matching length(::SymbolicUtils.Sym{Array})
Closest candidates are:
  length(::Core.SimpleVector) at essentials.jl:596
  length(::Base.MethodList) at reflection.jl:852
  length(::Core.MethodTable) at reflection.jl:938
  ...
Stacktrace:
 [1] top-level scope at REPL[5]:1

[shashi]

We still have to define methods on array typed variables.

We got started on this in https://github.com/JuliaSymbolics/SymbolicUtils.jl/tree/s/new-array but haven't yet got around to it. Let me know if you need it.

[shashi]

rebased, also thinking about a composable metadata system. #123

[shashi]

I'll close this for now as a duplicate of #16

maybe the documentation should be made clearer about ::T though.