fix bug in term ordering for small terms

Author: shashi

src/simplify.jl

@@ -115,12 +115,14 @@ function <ₑ(a::Term, b::Term)
         return a <ₑ operation(b)
     end
 
+    na = nameof(operation(a))
+    nb = nameof(operation(b))
+
     if 0 < arglength(a) <= 2 && 0 < arglength(b) <= 2
         # e.g. a < sin(a) < b ^ 2 < b
         @goto compare_args
     end
-    na = nameof(operation(a))
-    nb = nameof(operation(b))
+
     if na !== nb
         return na <ₑ nb
     elseif arglength(a) != arglength(b)
@@ -144,9 +146,11 @@ function <ₑ(a::Term, b::Term)
             # compare the numbers
             nums = zip(Iterators.filter(isnumber, aa),
                        Iterators.filter(isnumber, ab))
-            return any(a <ₑ b for (a, b) in nums)
+            if any(a <ₑ b for (a, b) in nums)
+                return true
+            end
         end
-        return na <ₑ nb
+        return na <ₑ nb # all args are equal, compare the name
     end
 end
 

test/basics.jl

@@ -92,5 +92,5 @@ end
     @syms a b
     @test repr(a+b) == "a + b"
     @test repr(-a) == "-a"
-    @test repr(-a + 3) == "3 + (-a)"
+    @test repr(-a + 3) == "(-a) + 3"
 end

test/order.jl

@@ -47,15 +47,19 @@ end
         @test !(b <ₑ f(2,b))
         for j in i+1:length(fs)
             g = fs[j]
-            @test !(g(a, b) <ₑ f(a, b)) && !(f(a, b) <ₑ g(a, b))
+            @test g(a, b) <ₑ f(a, b) && !(f(a, b) <ₑ g(a, b))
             @test istotal(f(a, b), g(a, b))
         end
     end
 end
 
-@testset "0-arg variable calls ordering" begin
+@testset "callable variable order" begin
     @syms z() ρ()
 
     @test -1z() <ₑ ρ()
     @test !(ρ() <ₑ -1z())
+
+    @syms a(t) b(t) t
+    @test a(t) <ₑ b(t)
+    @test !(b(t) <ₑ a(t))
 end

test/rulesets.jl

@@ -22,7 +22,7 @@ end
     @syms a::Integer b c d x::Real y::Number
     @test simplify(x - y) == x + -1*y
     @test simplify(x - sin(y)) == x + -1*sin(y)
-    @test simplify(-sin(x)) == -sin(x)
+    @test simplify(-sin(x)) == -1*sin(x)
     @test simplify(1 * x * 2) == 2 * x
     @test simplify(1 + x + 2) == 3 + x
     @test simplify(b*b) == b^2 # tests merge_repeats