Fix Lex comparison (#153)

* Fix Lex comparison

* fix

Author: blegat

src/comp.jl

@@ -99,6 +99,18 @@ function MP.compare(
             j += 1
         end
     end
+    @inbounds while i <= nvariables(x)
+        if x.z[i] > 0
+            return 1
+        end
+	i += 1
+    end
+    @inbounds while j <= nvariables(y)
+        if y.z[j] > 0
+            return -1
+        end
+	j += 1
+    end
     return 0
 end
 

test/comp.jl

@@ -10,6 +10,17 @@ import DynamicPolynomials: Commutative, CreationOrder # to test hygiene
     @polyvar x variable_order = order
     @test z != x
 end
+function _less(a, b)
+    @test a < b
+    @test b > a
+    @test compare(monomial(a), b) < 0
+    @test compare(b, monomial(a)) > 0
+end
+@testset "Issue 152" begin
+    @polyvar x y monomial_order=LexOrder
+    _less(x, x * y)
+    _less(x * y^2, x^2)
+end
 @testset "README example" begin
     function p(x, y, z)
         return sprint(