Handle conditionals and abs

Project.toml

@@ -12,6 +12,7 @@ DiffRules = "b552c78f-8df3-52c6-915a-8e097449b14b"
 Distributed = "8ba89e20-285c-5b6f-9357-94700520ee1b"
 DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"
 GeneralizedGenerated = "6b9d7cbe-bcb9-11e9-073f-15a7a543e2eb"
+IfElse = "615f187c-cbe4-4ef1-ba3b-2fcf58d6d173"
 LabelledArrays = "2ee39098-c373-598a-b85f-a56591580800"
 Latexify = "23fbe1c1-3f47-55db-b15f-69d7ec21a316"
 Libdl = "8f399da3-3557-5675-b5ff-fb832c97cbdb"

src/ModelingToolkit.jl

@@ -14,6 +14,7 @@ import GeneralizedGenerated
 import Libdl
 using DocStringExtensions
 using Base: RefValue
+import IfElse
 
 using RecursiveArrayTools
 
@@ -123,6 +124,7 @@ include("systems/reduction.jl")
 
 include("latexify_recipes.jl")
 include("build_function.jl")
+include("extra_functions.jl")
 
 export ODESystem, ODEFunction, ODEFunctionExpr, ODEProblemExpr
 export SDESystem, SDEFunction, SDEFunctionExpr, SDESystemExpr

src/differentials.jl

@@ -180,7 +180,7 @@ derivative(O::Constant, ::Any) = Constant(0)
 # Pre-defined derivatives
 import DiffRules
 for (modu, fun, arity) ∈ DiffRules.diffrules()
-    fun in [:*, :+] && continue # special
+    fun in [:*, :+, :abs] && continue # special
     for i ∈ 1:arity
 
         expr = if arity == 1

src/extra_functions.jl

@@ -0,0 +1,14 @@
+@register Base.conj(x)
+@register Base.getindex(x,i)
+@register Base.binomial(n,k)
+@register Base.copysign(x,y)
+
+@register Base.signbit(x)
+ModelingToolkit.derivative(::typeof(signbit), args::NTuple{1,Any}, ::Val{1}) = 0
+
+ModelingToolkit.derivative(::typeof(abs), args::NTuple{1,Any}, ::Val{1}) = IfElse.ifelse(signbit(args[1]),-one(args[1]),one(args[1]))
+
+@register IfElse.ifelse(x,y,z)
+ModelingToolkit.derivative(::typeof(IfElse.ifelse), args::NTuple{3,Any}, ::Val{1}) = 0
+ModelingToolkit.derivative(::typeof(IfElse.ifelse), args::NTuple{3,Any}, ::Val{2}) = IfElse.ifelse(args[1],1,0)
+ModelingToolkit.derivative(::typeof(IfElse.ifelse), args::NTuple{3,Any}, ::Val{3}) = IfElse.ifelse(args[1],0,1)

src/function_registration.jl

@@ -99,18 +99,10 @@ for fun ∈ [:<, :>, :(==), :&, :|, :div]
     @eval @register $sig
 end
 
-# ifelse
-#@register Base.ifelse(cond,t,f)
-
 # special cases
 Base.:^(x::Expression,y::T) where T <: Integer = Operation(Base.:^, Expression[x, y])
 Base.:^(x::Expression,y::T) where T <: Rational = Operation(Base.:^, Expression[x, y])
 
-@register Base.conj(x)
-@register Base.getindex(x,i)
-@register Base.binomial(n,k)
-@register Base.copysign(x,y)
-
 Base.getindex(x::Operation,i::Int64) = Operation(getindex,[x,i])
 Base.one(::Operation) = 1