handle conversion from number to Sym tf (#25)

* handle conversion from number to Sym tf

* fix

* more robust SymPy -> Symbolics translation

Author: baggepinnen

.github/workflows/ci.yml

@@ -1,6 +1,5 @@
 name: CI
 on:
-  - push
   - pull_request
 jobs:
   test:

src/SymbolicControlSystems.jl

@@ -89,27 +89,31 @@ function ControlSystemsBase.tf(sys::Sym, h = nothing)
     # d = d.monic() # Don't do this here
     if h === nothing || h isa Continuous
         d = sp.Poly(d, s)
-        n = n isa Number ? n : sp.Poly(n, s)
+        n = n isa Number ? 1.0*n : sp.Poly(n, s)
         tf(expand_coeffs(n, s), expand_coeffs(d, s))
     else
         d = sp.Poly(d, z)
-        n = n isa Number ? n : sp.Poly(n, z)
+        n = n isa Number ? 1.0*n : sp.Poly(n, z)
         tf(expand_coeffs(n, z), expand_coeffs(d, z), h)
     end
 end
 
 function expand_coeffs(n, var; numeric = false)
-    n = sp.Poly(n, var)
-    deg = n.degree() |> Float64 |> Int
-    c = n.all_coeffs() # This fails if the coeffs are symbolic
-    numeric && (c = Float64.(c))
-    [c; zeros(eltype(c), deg - length(c) + 1)]
+    if n == 0
+        [0.0]
+    else
+        n = sp.Poly(n, var)
+        deg = n.degree() |> Float64 |> Int
+        c = n.all_coeffs() # This fails if the coeffs are symbolic
+        numeric && (c = Float64.(c))
+        [c; zeros(eltype(c), deg - length(c) + 1)]
+    end
 end
 expand_coeffs(n::Real, args...; numeric = false) = n
 
 function ControlSystemsBase.tf(sys::NumOrDiv, h = nothing)
-    sp = Symb.symbolics_to_sympy(sys)
-    G = tf(sp, h)
+    sys_sp = Symb.symbolics_to_sympy(sys)
+    G = h === nothing || h === Continuous() ? tf(sys_sp) : tf(sys_sp, h)
     tf(to_num.(numvec(G)[]), to_num.(denvec(G)[]), G.timeevol)
 end
 
@@ -144,7 +148,8 @@ function to_num(x::Sym)::Num
     try
         return Float64(x)
     catch
-        Symb.Num(Symb.variable(Symbol(x); T=Real))
+        # Symb.Num(Symb.variable(Symbol(x); T=Real))
+        Symb.parse_expr_to_symbolic(Meta.parse(string(x)), Main)
     end
 end
 

test/runtests.jl

@@ -4,7 +4,7 @@ using ControlSystemsBase
 s = SymbolicControlSystems.s
 z = SymbolicControlSystems.z
 import Symbolics
-import Symbolics: Num
+using Symbolics: Num
 using LinearAlgebra
 isinteractive() && (Base.active_repl.options.hint_tab_completes = false) # This messes with sympy https://discourse.julialang.org/t/sympy-makes-repl-to-stuck/124814/6
 
@@ -96,6 +96,13 @@ end
         @test_both tf([b, a], [1, c, 1])  (b*s + a)/(s^2 + c*s + 1)
         @test_both tf([b, a], [1, c, 1], 0.1)  (b*z + a)/(z^2 + c*z + 1)
 
+
+        @syms T
+        @test convert(typeof(tf(1, [T, 1])), 0) == tf(0)
+        @test_nowarn [0 tf(1, [T, 1]); 0 tf(1)]
+        @test [tf(0) tf(1, [T, 1])] == [0 tf(1, [T, 1])]
+
+
     end