Merge pull request #161 from JuliaSymbolics/myb/trans

Ensure transitivity in tree ordering

Author: shashi

.gitignore

@@ -0,0 +1,5 @@
+*.jl.*.cov
+*.jl.cov
+*.jl.mem
+Manifest.toml
+/docs/build/

Project.toml

@@ -1,7 +1,7 @@
 name = "SymbolicUtils"
 uuid = "d1185830-fcd6-423d-90d6-eec64667417b"
 authors = ["Shashi Gowda"]
-version = "0.7.2"
+version = "0.7.3"
 
 [deps]
 AbstractAlgebra = "c3fe647b-3220-5bb0-a1ea-a7954cac585d"

src/ordering.jl

@@ -13,39 +13,13 @@ function <ₑ(a, b)
     if !istree(a) && !istree(b)
         T = typeof(a)
         S = typeof(b)
-        T===S ? isless(a, b) : nameof(T) < nameof(S)
+        return T===S ? isless(a, b) : nameof(T) < nameof(S)
     elseif istree(b) && !istree(a)
-        args = arguments(b)
-        if length(args) === 2
-            n1, n2 = !is_literal_number(args[1]) , !is_literal_number(args[2])
-            if n1 && n2
-                # both subterms are terms, so it's definitely firster
-                return true
-            elseif n1
-                return isequal(a, args[1]) || a <ₑ args[1]
-            elseif n2
-                return isequal(a, args[2]) || a <ₑ args[2]
-            else
-                # both arguments are not numbers
-                # This case when a <ₑ Term(^, [1,-1])
-                # so this term should go to the left.
-                return false
-            end
-        elseif length(args) === 1
-            # make sure a < sin(a) < b^2 < b
-            if isequal(a, args[1])
-                return true # e.g sin(a)*a should become a*sin(a)
-            else
-                return a<ₑargs[1]
-            end
-        else
-            # variables to the right
-            return false
-        end
+        return true
     elseif istree(a) && istree(b)
-        cmp_term_term(a,b)
+        return cmp_term_term(a,b)
     else
-        !(b <ₑ a)
+        return !(b <ₑ a)
     end
 end
 

test/order.jl

@@ -1,5 +1,6 @@
 using Test
-using SymbolicUtils: <ₑ
+using Combinatorics
+using SymbolicUtils: <ₑ, arguments
 SymbolicUtils.show_simplified[] = false
 
 @syms a b c
@@ -26,7 +27,7 @@ end
 @test istotal(b*a, a)
 @test istotal(a, b*a)
 @test !(b*a <ₑ b+a)
-@test Term(^, [1,-1]) <ₑ a
+@test a <ₑ Term(^, [1,-1])
 @test istotal(a, Term(^, [1,-1]))
 
 @testset "operator order" begin
@@ -56,8 +57,7 @@ end
 @testset "callable variable order" begin
     @syms z() ρ()
 
-    @test -1z() <ₑ ρ()
-    @test !(ρ() <ₑ -1z())
+    @test istotal(ρ(), -1z())
 
     @syms a(t) b(t) t
     @test a(t) <ₑ b(t)
@@ -72,7 +72,7 @@ end
     @syms x y
 
     @test x <ₑ (3 + x) && !((3 + x) <ₑ x)
-    @test x^2 <ₑ y && !(y <ₑ x^2)
+    @test istotal(y, x^2)
 
     # a nice consequence
     @test simplify(x/(x+3) + 3/(x+3)) == 1
@@ -84,3 +84,11 @@ end
     @test Term(^, [a, -1]) <ₑ (a + 2)
     @test !((a + 2) <ₑ Term(^, [a, -1]))
 end
+
+@testset "transitivity" begin
+    # issue #160
+    @syms σ x y z
+    expr = σ*sin(x + -1y)*(sin(z)^(-1))*(-1x + y)
+    args = arguments(expr)
+    @test all(((a, b), )->a <ₑ b,  combinations(args, 2))
+end