Merge pull request #1273 from AayushSabharwal/as/derivatives

fix: define derivatives of ssqrt, scbrt, slog

src/solver/solve_helpers.jl

@@ -37,6 +37,8 @@ function ssqrt(n)
     end
 end
 
+derivative(::typeof(ssqrt), args...) = substitute(derivative(sqrt, args...), sqrt => ssqrt)
+
 function scbrt(n)
     n = unwrap(n)
 
@@ -53,6 +55,8 @@ function scbrt(n)
     end
 end
 
+derivative(::typeof(scbrt), args...) = substitute(derivative(cbrt, args...), cbrt => scbrt)
+
 function slog(n)
     n = unwrap(n)
 
@@ -67,6 +71,8 @@ function slog(n)
     return term(slog, n)
 end
 
+derivative(::typeof(slog), args...) = substitute(derivative(log, args...), log => slog)
+
 const RootsOf = (SymbolicUtils.@syms roots_of(poly,var))[1]
 
 Base.show(io::IO, f::typeof(ssqrt)) = print(io, "√")

test/diff.jl

@@ -398,3 +398,12 @@ let
         @test_throws TypeError Symbolics.derivative(f, Val(rand(Int)))
     end
 end
+
+# Check ssqrt, scbrt, slog
+let
+    @variables x
+    D = Differential(x)
+    @test isequal(expand_derivatives(D(Symbolics.ssqrt(1 + x ^ 2))), simplify((2x) / (2Symbolics.ssqrt(1 + x^2))))
+    @test isequal(expand_derivatives(D(Symbolics.scbrt(1 + x ^ 2))), simplify((2x) / (3Symbolics.scbrt(1 + x^2)^2)))
+    @test isequal(expand_derivatives(D(Symbolics.slog(1 + x ^ 2))), simplify((2x) / (1 + x ^ 2)))
+end