add parameter call finding helper

Author: ChrisRackauckas

src/ModelingToolkit.jl

@@ -3,6 +3,7 @@ module ModelingToolkit
 export Operation, Expression
 export calculate_jacobian, generate_jacobian, generate_function
 export independent_variables, dependent_variables, parameters
+export find_parameter_calls
 export @register
 
 

src/equations.jl

@@ -10,3 +10,14 @@ Base.:(==)(a::Equation, b::Equation) = isequal((a.lhs, a.rhs), (b.lhs, b.rhs))
 Base.:~(lhs::Expression, rhs::Expression) = Equation(lhs, rhs)
 Base.:~(lhs::Expression, rhs::Number    ) = Equation(lhs, rhs)
 Base.:~(lhs::Number    , rhs::Expression) = Equation(lhs, rhs)
+
+function find_parameter_calls(O::Operation,p_calls=Variable[])
+  if O.op isa Variable && O.op.known && !isempty(O.args)
+      push!(p_calls,O.op)
+      find_parameter_calls.(O.args,(p_calls,))
+  else
+      find_parameter_calls.(O.args,(p_calls,))
+  end
+  p_calls
+end
+find_parameter_calls(O,p_calls) = nothing

src/variables.jl

@@ -1,4 +1,4 @@
-export Variable, @variables, @parameters, @dependent_parameters
+export Variable, @variables, @parameters
 
 
 struct Variable <: Function

test/find_parameter_calls.jl

@@ -0,0 +1,14 @@
+using ModelingToolkit
+using Test
+
+# Define some variables
+@parameters t σ ρ β, α(..)
+@variables x(t) y(t) z(t)
+@derivatives D'~t
+
+eq1 = D(x) ~ σ*(y-x)
+eq2 = D(x) ~ α(t-2)*(y-x)
+
+find_parameter_calls(eq1.rhs,Variable[])
+r = find_parameter_calls(eq2.rhs,Variable[])
+!isempty(r) && r[1].name == :α

test/runtests.jl

@@ -3,4 +3,5 @@ using ModelingToolkit, Test
 @testset "Parsing Test" begin include("variable_parsing.jl") end
 @testset "Differentiation Test" begin include("derivatives.jl") end
 @testset "Simplify Test" begin include("simplify.jl") end
+@testset "Parameter Call Finding Test" begin include("find_parameter_calls.jl") end
 @testset "System Construction Test" begin include("system_construction.jl") end