inverse W

Author: ChrisRackauckas

src/operations.jl

@@ -57,3 +57,7 @@ function find_replace!(O::Operation,x::Variable,y::Expression)
         end
     end
 end
+
+# For inv
+Base.convert(::Type{Operation},x::Int) = Operation(identity,Expression[Constant(x)])
+Base.convert(::Type{Operation},x::Variable) = Operation(identity,Expression[x])

src/simplify.jl

@@ -16,7 +16,7 @@ function _simplify_constants(O)
         # If any variable is `Constant(0)`, zero the whole thing
         # If any variable is `Constant(1)`, remove that `Constant(1)` unless
         # they are all `Constant(1)`, in which case simplify to a single variable
-        if any(x->typeof(x)<:Variable && isequal(x,Constant(0)),O.args)
+        if any(x->typeof(x)<:Variable && (isequal(x,Constant(0)) || isequal(x,Constant(-0))),O.args)
             return Constant(0)
         elseif any(x->typeof(x)<:Variable && isequal(x,Constant(1)),O.args)
             idxs = find(x->typeof(x)<:Variable && isequal(x,Constant(1)),O.args)
@@ -31,9 +31,9 @@ function _simplify_constants(O)
         else
             return O
         end
-    elseif Symbol(O.op) == :+ && any(x->typeof(x)<:Variable && isequal(x,Constant(0)),O.args)
+    elseif Symbol(O.op) == :+ && any(x->typeof(x)<:Variable && (isequal(x,Constant(0)) || isequal(x,Constant(-0))),O.args)
         # If there are Constant(0)s in a big `+` expression, get rid of them
-        idxs = find(x->typeof(x)<:Variable && isequal(x,Constant(0)),O.args)
+        idxs = find(x->typeof(x)<:Variable && (isequal(x,Constant(0)) || isequal(x,Constant(-0))),O.args)
         _O = Operation(O.op,O.args[1:length(O.args) .∉ (idxs,)])
         if isempty(_O.args)
             return Constant(0)
@@ -42,6 +42,8 @@ function _simplify_constants(O)
         else
             return O
         end
+    elseif O.op == identity
+        return O.args[1]
     else
         return O
     end

test/system_construction.jl

@@ -18,8 +18,8 @@ SciCompDSL.generate_ode_function(de)
 jac_expr = SciCompDSL.generate_ode_jacobian(de)
 jac = SciCompDSL.calculate_jacobian(de)
 f = DiffEqFunction(de)
-I - jac
-@test_broken inv(I - jac)
+W = I - jac
+simplify_constants.(inv(W))
 
 # Differential equation with automatic extraction of variables on rhs
 de2 = DiffEqSystem(eqs, [t])