feat: add

Author: vyudu

src/ModelingToolkit.jl

@@ -286,7 +286,7 @@ export toexpr, get_variables
 export simplify, substitute
 export build_function
 export modelingtoolkitize
-export generate_initializesystem, Initial
+export generate_initializesystem, Initial, isInitial
 
 export alg_equations, diff_equations, has_alg_equations, has_diff_equations
 export get_alg_eqs, get_diff_eqs, has_alg_eqs, has_diff_eqs

src/systems/abstractsystem.jl

@@ -717,6 +717,22 @@ function add_initialization_parameters(sys::AbstractSystem)
     return sys
 end
 
+"""
+Returns true if the variable or parameter `var` is of the form `Initial(x)`.
+"""
+function isInitial(var)
+    var = unwrap(var)
+    if iscall(var)
+        operation(var) isa Initial && return true
+        if operation(var) === getindex
+            operation(arguments(var)[1]) isa Initial && return true
+        end
+    else
+        return false
+    end
+    return false
+end
+
 """
 $(TYPEDSIGNATURES)
 

test/variable_utils.jl

@@ -145,3 +145,16 @@ end
         @test isequal(parse_variable(sys, str), var)
     end
 end
+
+@testset "isInitial" begin
+    t = ModelingToolkit.to_nounits
+    @variables x(t) z(t)[1:5]
+    @parameters a b c[1:4]
+    @test isInitial(Initial(z))
+    @test isInitial(Initial(x))
+    @test isInitial(Initial(a))
+    @test isInitial(Initial(z[1]))
+    @test isInitial(Initial(c[4]))
+    @test !isInitial(c)
+    @test !isInitial(x)
+end