toodesystem -> convert_system

Author: YingboMa

src/ModelingToolkit.jl

@@ -136,7 +136,7 @@ include("systems/alias_elimination.jl")
 include("structural_transformation/StructuralTransformations.jl")
 @reexport using .StructuralTransformations
 
-export ODESystem, ODEFunction, ODEFunctionExpr, ODEProblemExpr, toodesystem
+export ODESystem, ODEFunction, ODEFunctionExpr, ODEProblemExpr, convert_system
 export DAEFunctionExpr, DAEProblemExpr
 export SDESystem, SDEFunction, SDEFunctionExpr, SDESystemExpr
 export SystemStructure

src/systems/abstractsystem.jl

@@ -737,40 +737,3 @@ end
 function connect(syss...)
     connect(promote_connect_type(map(get_connection_type, syss)...), syss...)
 end
-
-###
-### system promotion
-###
-
-# We have a stand-alone function to convert a `NonlinearSystem` or `ODESystem`
-# to an `ODESystem` to connect systems, and we later can reply on
-# `structural_simplify` to convert `ODESystem`s to `NonlinearSystem`s.
-function toodesystem(sys, t; name=nameof(sys))
-    isempty(observed(sys)) || throw(ArgumentError("`toodesystem` cannot handle reduced model (i.e. observed(sys) is non-empty)."))
-    t = value(t)
-    varmap = Dict()
-    sts = states(sys)
-    newsts = similar(sts, Any)
-    for (i, s) in enumerate(sts)
-        if istree(s)
-            args = arguments(s)
-            length(args) == 1 || throw(InvalidSystemException("Illegal state: $s. The state can have at most one argument like `x(t)`."))
-            arg = args[1]
-            if isequal(arg, t)
-                newsts[i] = s
-                continue
-            end
-            ns = operation(s)(t)
-            newsts[i] = ns
-            varmap[s] = ns
-        else
-            ns = indepvar2depvar(s, t)
-            newsts[i] = ns
-            varmap[s] = ns
-        end
-    end
-    sub = Base.Fix2(substitute, varmap)
-    neweqs = map(sub, equations(sys))
-    defs = Dict(sub(k) => sub(v) for (k, v) in defaults(sys))
-    return ODESystem(neweqs, t, newsts, parameters(sys); defaults=defs, name=name)
-end

src/systems/diffeqs/odesystem.jl

@@ -300,3 +300,42 @@ function collect_differential_variables(sys::ODESystem)
     end
     return diffvars
 end
+
+# We have a stand-alone function to convert a `NonlinearSystem` or `ODESystem`
+# to an `ODESystem` to connect systems, and we later can reply on
+# `structural_simplify` to convert `ODESystem`s to `NonlinearSystem`s.
+"""
+$(TYPEDSIGNATURES)
+
+Convert a `NonlinearSystem` to an `ODESystem` or converts an `ODESystem` to a
+new `ODESystem` with a different independent variable.
+"""
+function convert_system(::Type{<:ODESystem}, sys, t; name=nameof(sys))
+    isempty(observed(sys)) || throw(ArgumentError("`convert_system` cannot handle reduced model (i.e. observed(sys) is non-empty)."))
+    t = value(t)
+    varmap = Dict()
+    sts = states(sys)
+    newsts = similar(sts, Any)
+    for (i, s) in enumerate(sts)
+        if istree(s)
+            args = arguments(s)
+            length(args) == 1 || throw(InvalidSystemException("Illegal state: $s. The state can have at most one argument like `x(t)`."))
+            arg = args[1]
+            if isequal(arg, t)
+                newsts[i] = s
+                continue
+            end
+            ns = operation(s)(t)
+            newsts[i] = ns
+            varmap[s] = ns
+        else
+            ns = indepvar2depvar(s, t)
+            newsts[i] = ns
+            varmap[s] = ns
+        end
+    end
+    sub = Base.Fix2(substitute, varmap)
+    neweqs = map(sub, equations(sys))
+    defs = Dict(sub(k) => sub(v) for (k, v) in defaults(sys))
+    return ODESystem(neweqs, t, newsts, parameters(sys); defaults=defs, name=name)
+end

test/nonlinearsystem.jl

@@ -100,10 +100,10 @@ connected = NonlinearSystem([s ~ a + lorenz1.x
 using OrdinaryDiffEq
 @variables t
 D = Differential(t)
-@named subsys = toodesystem(lorenz1, t)
+@named subsys = convert_system(ODESystem, lorenz1, t)
 @named sys = ODESystem([D(subsys.x) ~ subsys.x + subsys.x], t, systems=[subsys])
 sys = structural_simplify(sys)
 prob = ODEProblem(sys, [subsys.x => 1, subsys.z => 2.0], (0, 1.0), [subsys.σ=>1,subsys.ρ=>2,subsys.β=>3])
 sol = solve(prob, Rodas5())
 @test sol[subsys.x] + sol[subsys.y] - sol[subsys.z] ≈ sol[subsys.u]
-@test_throws ArgumentError toodesystem(sys, t)
+@test_throws ArgumentError convert_system(ODESystem, sys, t)