Support Symbolic Arrays of arbitrary length

docs/src/basics/MTKLanguage.md

@@ -63,13 +63,14 @@ end
     @structural_parameters begin
         f = sin
         N = 2
+        M = 3
     end
     begin
         v_var = 1.0
     end
     @variables begin
         v(t) = v_var
-        v_array(t)[1:2, 1:3]
+        v_array(t)[1:N, 1:M]
         v_for_defaults(t)
     end
     @extend ModelB(; p1)
@@ -301,7 +302,7 @@ end
 
     For more examples of usage, checkout [ModelingToolkitStandardLibrary.jl](https://github.com/SciML/ModelingToolkitStandardLibrary.jl/)
 
-## More on `Model.structure`
+## [More on `Model.structure`](@id model_structure)
 
 `structure` stores metadata that describes composition of a model. It includes:
 
@@ -324,17 +325,57 @@ For example, the structure of `ModelC` is:
 julia> ModelC.structure
 Dict{Symbol, Any} with 10 entries:
   :components            => Any[Union{Expr, Symbol}[:model_a, :ModelA], Union{Expr, Symbol}[:model_array_a, :ModelA, :(1:N)], Union{Expr, Symbol}[:model_array_b, :ModelA, :(1:N)]]
-  :variables             => Dict{Symbol, Dict{Symbol, Any}}(:v=>Dict(:default=>:v_var, :type=>Real), :v_array=>Dict(:type=>Real, :size=>(2, 3)), :v_for_defaults=>Dict(:type=>Real))
+  :variables             => Dict{Symbol, Dict{Symbol, Any}}(:v=>Dict(:default=>:v_var, :type=>Real), :v_for_defaults=>Dict(:type=>Real))
   :icon                  => URI("https://github.com/SciML/SciMLDocs/blob/main/docs/src/assets/logo.png")
-  :kwargs                => Dict{Symbol, Dict}(:f=>Dict(:value=>:sin), :N=>Dict(:value=>2), :v=>Dict{Symbol, Any}(:value=>:v_var, :type=>Real), :v_array=>Dict{Symbol, Union{Nothing, UnionAll}}(:value=>nothing, :type=>AbstractArray{Real}), :v_for_defaults=>Dict{Symbol, Union{Nothing, DataType}}(:value=>nothing, :type=>Real), :p1=>Dict(:value=>nothing))
-  :structural_parameters => Dict{Symbol, Dict}(:f=>Dict(:value=>:sin), :N=>Dict(:value=>2))
+  :kwargs                => Dict{Symbol, Dict}(:f => Dict(:value => :sin), :N => Dict(:value => 2), :M => Dict(:value => 3), :v => Dict{Symbol, Any}(:value => :v_var, :type => Real), :v_for_defaults => Dict{Symbol, Union{Nothing, DataType}}(:value => nothing, :type => Real), :p1 => Dict(:value => nothing)),
+  :structural_parameters => Dict{Symbol, Dict}(:f => Dict(:value => :sin), :N => Dict(:value => 2), :M => Dict(:value => 3))
   :independent_variable  => t
   :constants             => Dict{Symbol, Dict}(:c=>Dict{Symbol, Any}(:value=>1, :type=>Int64, :description=>"Example constant."))
   :extend                => Any[[:p2, :p1], Symbol("#mtkmodel__anonymous__ModelB"), :ModelB]
   :defaults              => Dict{Symbol, Any}(:v_for_defaults=>2.0)
   :equations             => Any["model_a.k ~ f(v)"]
 ```
 
+### Different ways to define symbolics arrays:
+
+`@mtkmodel` supports symbolics arrays in both `@parameters` and `@variables`.
+Using a structural parameters, symbolic arrays of arbitrary lengths can be defined.
+Refer the following example for different ways to define symbolic arrays.
+
+```@example mtkmodel-example
+@mtkmodel ModelWithArrays begin
+    @structural_parameters begin
+        N = 2
+        M = 3
+    end
+    @parameters begin
+        p1[1:4]
+        p2[1:N]
+        p3[1:N, 1:M] = 10,
+        [description = "A multi-dimensional array of arbitrary length with description"]
+        (p4[1:N, 1:M] = 10),
+        [description = "An alternate syntax for p3 to match the syntax of vanilla parameters macro"]
+    end
+    @variables begin
+        v1(t)[1:2] = 10, [description = "An array of variable `v1`"]
+        v2(t)[1:3] = [1, 2, 3]
+    end
+end
+```
+
+The size of symbolic array can be accessed via `:size` key, along with other metadata (refer [More on `Model.structure`](@ref model_structure))
+of the symbolic variable.
+
+```julia
+julia> ModelWithArrays.structure
+Dict{Symbol, Any} with 5 entries:
+    :variables => Dict{Symbol, Dict{Symbol, Any}}(:v2 => Dict(:value => :([1, 2, 3]), :type => Real, :size => (3,)), :v1 => Dict(:value => :v1, :type => Real, :description => "An array of variable `v1`", :size => (2,)))
+    :kwargs => Dict{Symbol, Dict}(:p2 => Dict{Symbol, Any}(:value => nothing, :type => Real, :size => (:N,)), :v1 => Dict{Symbol, Any}(:value => :v1, :type => Real, :description => "An array of variable `v1`", :size => (2,)), :N => Dict(:value => 2), :M => Dict(:value => 3), :p4 => Dict{Symbol, Any}(:value => 10, :type => Real, :description => "An alternate syntax for p3 to match the syntax of vanilla parameters macro", :size => (:N, :M)), :v2 => Dict{Symbol, Any}(:value => :([1, 2, 3]), :type => Real, :size => (3,)), :p1 => Dict{Symbol, Any}(:value => nothing, :type => Real, :size => (4,)), :p3 => Dict{Symbol, Any}(:value => :p3, :type => Real, :description => "A multi-dimensional array of arbitrary length with description", :size => (:N, :M)))
+    :structural_parameters => Dict{Symbol, Dict}(:N => Dict(:value => 2), :M => Dict(:value => 3))
+    :independent_variable => :t
+    :parameters => Dict{Symbol, Dict{Symbol, Any}}(:p2 => Dict(:value => nothing, :type => Real, :size => (:N,)), :p4 => Dict(:value => 10, :type => Real, :description => "An alternate syntax for p3 to match the syntax of vanilla parameters macro", :size => (:N, :M)), :p1 => Dict(:value => nothing, :type => Real, :size => (4,)), :p3 => Dict(:value => :p3, :type => Real, :description => "A multi-dimensional array of arbitrary length with description", :size => (:N, :M)))), false)
+```
+
 ### Using conditional statements
 
 #### Conditional elements of the system