Merge pull request #238 from JuliaDiffEq/myb/n-ary

Add n-ary *, + rules

Project.toml

@@ -1,7 +1,7 @@
 name = "ModelingToolkit"
 uuid = "961ee093-0014-501f-94e3-6117800e7a78"
 authors = ["Chris Rackauckas <[email protected]>"]
-version = "1.2.2"
+version = "1.2.3"
 
 [deps]
 DiffEqBase = "2b5f629d-d688-5b77-993f-72d75c75574e"

src/differentials.jl

@@ -99,6 +99,7 @@ derivative(O::Operation, idx) = derivative(O.op, (O.args...,), Val(idx))
 # Pre-defined derivatives
 import DiffRules, SpecialFunctions, NaNMath
 for (modu, fun, arity) ∈ DiffRules.diffrules()
+    fun in [:*, :+] && continue # special
     for i ∈ 1:arity
         @eval function derivative(::typeof($modu.$fun), args::NTuple{$arity,Any}, ::Val{$i})
             M, f = $(modu, fun)
@@ -109,9 +110,8 @@ for (modu, fun, arity) ∈ DiffRules.diffrules()
     end
 end
 
-derivative(::typeof(+), args::NTuple{T,Operation}, ::Val{i}) where {T,i} = args[i]
-derivative(::typeof(+), args::Tuple{Operation,Operation}, ::Val{1}) = args[1]
-derivative(::typeof(+), args::Tuple{Operation,Operation}, ::Val{2}) = args[2]
+derivative(::typeof(+), args::NTuple{N,Any}, ::Val) where {N} = 1
+derivative(::typeof(*), args::NTuple{N,Any}, ::Val{i}) where {N,i} = Operation(*, deleteat!(collect(args), i))
 
 function count_order(x)
     @assert !(x isa Symbol) "The variable $x must have an order of differentiation that is greater or equal to 1!"

test/derivatives.jl

@@ -31,7 +31,7 @@ dsinsin = D(sin(sin(t)))
 d1 = D(sin(t)*t)
 d2 = D(sin(t)*cos(t))
 @test isequal(expand_derivatives(d1), t*cos(t)+sin(t))
-@test isequal(expand_derivatives(d2), simplify_constants(cos(t)*cos(t)+sin(t)*(-1*sin(t))))
+@test isequal(expand_derivatives(d2), simplify_constants(cos(t)*cos(t)+(sin(t)*-1)*sin(t)))
 
 eqs = [0 ~ σ*(y-x),
        0 ~ x*(ρ-z)-y,
@@ -60,3 +60,7 @@ jac = calculate_jacobian(sys)
 @test isequal(expand_derivatives(D(2t)), 2)
 @test isequal(expand_derivatives(D(2x)), 2D(x))
 @test isequal(expand_derivatives(D(x^2)), simplify_constants(2 * x * D(x)))
+
+# n-ary * and +
+isequal(ModelingToolkit.derivative(Operation(*, [x, y, z*ρ]), 1), y*(z*ρ))
+isequal(ModelingToolkit.derivative(Operation(+, [x*y, y, z]), 1), 1)