exprs_occur_in

Author: shashi

src/direct.jl

@@ -79,6 +79,16 @@ function jacobian_sparsity(du, u)
     sparse(I, J, true, length(du), length(u))
 end
 
+"""
+    exprs_occur_in(exprs::Vector, expr)
+
+Return an array of booleans `finds` where `finds[i]` is true if `exprs[i]` occurs in `expr`
+false otherwise.
+"""
+function exprs_occur_in(exprs::Vector, expr)
+    vec(jacobian_sparsity([expr], exprs))
+end
+
 """
 ```julia
 hessian(O, vars::AbstractVector; simplify = true)

test/direct.jl

@@ -36,6 +36,11 @@ reference_jac = sparse(ModelingToolkit.jacobian(du, [x,y,z]))
 
 @test findnz(ModelingToolkit.jacobian_sparsity(du, [x,y,z]))[[1,2]] == findnz(reference_jac)[[1,2]]
 
+let
+    @variables t x(t) y(t) z(t)
+    @test ModelingToolkit.exprs_occur_in([x,y,z], x^2*y) == [true, true, false]
+end
+
 @test isequal(ModelingToolkit.sparsejacobian(du, [x,y,z]), reference_jac)
 
 using ModelingToolkit