Fix typo

Author: YingboMa

src/ModelingToolkit.jl

@@ -181,7 +181,7 @@ export Term, Sym
 export SymScope, LocalScope, ParentScope, GlobalScope
 export independent_variables, independent_variable, states, parameters, equations, controls,
        observed, structure, full_equations
-export structural_simplify, expand_connections
+export structural_simplify, expand_connections, linearize
 export DiscreteSystem, DiscreteProblem
 
 export calculate_jacobian, generate_jacobian, generate_function

src/inputoutput.jl

@@ -270,7 +270,7 @@ function inputs_to_parameters!(state::TransformationState, check_bound = true)
             push!(new_fullvars, v)
         end
     end
-    ninputs == 0 && return state
+    ninputs == 0 && return state, 1:0
 
     nvars = ndsts(graph) - ninputs
     new_graph = BipartiteGraph(nsrcs(graph), nvars, Val(false))

src/systems/abstractsystem.jl

@@ -967,7 +967,6 @@ function structural_simplify(sys::AbstractSystem; simplify = false, kwargs...)
     return sys
 end
 
-export linearize
 # TODO: The order of the states and equations should match so that the Jacobians are ẋ = Ax
 function linearize(sys::AbstractSystem, inputs, outputs; simplify = false, kwargs...)
     sys = expand_connections(sys)
@@ -1026,7 +1025,7 @@ function linearize(sys::AbstractSystem, inputs, outputs; simplify = false, kwarg
     return sys, lin_fun
 end
 
-function markio!(state::TearingState, inputs, outputs)
+function markio!(state, inputs, outputs)
     fullvars = state.fullvars
     inputset = Set(inputs)
     outputset = Set(outputs)

test/linearize.jl

@@ -80,4 +80,5 @@ ModelingToolkit.unbound_inputs(pid)
 @unpack reference, measurement, ctr_output = pid
 lin = linearize(pid, [reference.u, measurement.u], [ctr_output.u])
 lin, lin_fun = linearize(pid, [reference.u, measurement.u], [ctr_output.u]);
+prob = ODEProblem(lin, [], (0.0, 1.0))
 lin_fun(prob.u0, prob.p, 0.0)